GUIDELINES
FOR THE USE OF ENCAPSULANTS
ON ASBESTOS-CONTAINING MATERIALS
Office of Toxic Substances,
United States Environmental Protection Agency
February 23, 1981
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NOTE
Mention of any product or company names does not constitute
recommendation or endorsement by EPA or by any of its
contractors.
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T
Introduction
Chapter One.
Chapter Two.
Chapter Three,
Chapter Four.
Chapter Five:
TABLE OF CONTENTS
Advantages and Disadvantages
of the Use of Encapsulants
The Choice Between Bridging
and Penetrating Encapsulants
Choosing the Right Encapsulant
Latex Paints: For Use Only
on Cementitious Materials
Encapsulant Application
12
19
24
27
Appendix A:
Appendix B:
EPA Regional Asbestos Coordinators
A Test which Indicates Whether
Friable Asbestos-Containing Material
Can Sustain the Weight of an
Encapsulant
36
37
Tables:
1. Appropriate Situations for the Use of Encapsulants
11
2. Comparison of Bridging and Penetrating Encapsulants
18
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INTRODUCTION
As part of its program to address the problems caused by friable
asbestos-containing materials in buildings, the Environmental
Protection Agency has written these Guidelines for the Use of
Encapsulants on Asbestos-Containing Materials. The practice of
applying an encapsulant to asbestos-containing materials in
buildings in order to prevent or reduce the release of asbestos
fibers is called encapsulation.
The first chapter of this document discusses the advantages and
disadvantages of encapsulation. It is written primarily for
building owners and school administrators who have identified
asbestos problems, and is intended to help them decide whether
encapsulation is appropriate in their buildings.
The rest of the document discusses the points to consider when
choosing an encapsulant and the techniques to use when applying
it. This information should be useful to contractors who are
performing encapsulation jobs, as well as to building owners and
school administrators who are preparing contract documents for
encapsulation work or are monitoring work in progress.
The entire document should be used in conjunction with another
EPA publication entitled Asbestos-Containing Materials in School
Buildings; A Guidance Document. EPA strongly advises that
anyone concerned with asbestos problems in buildings consult
Asbestos-Containing Materials in School Buildings; A Guidance
Document, which discusses in detail the advantages and
disadvantages of various ways to prevent or reduce exposure to
asbestos.
Another EPA document, Guidelines for Removal of Friable Asbestos-
Containing Material, discusses in detail proper work practices
and worker protection procedures which apply to removal and
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encapsulation jobs. To obtain copies of Asbestos-Containing
Materials in School Buildings; A Guidance Document or Guidelines
for Removal of Friable Asbestos-Containing Material, call toll
free 800-424-9065 (in Washington, DC, 554-1404).
Persons interested in identifying a specific encapsulant should
contact the EPA's Regional Asbestos Coordinators, listed in
Appendix A to this document (page 36). The Asbestos Coordinators
can provide information on commercially available encapsulants,
answer questions, offer individual guidance, and discuss recent
developments with regard to asbestos in buildings. Any
contractor, school administrator, or building owner is encouraged
to call the Asbestos Coordinator for his or her Region.
This guidance document was prepared by the Chemical Control
Division of EPA's Office of Toxic Substances with the help of
Mr. William Mirick of Battelle Columbus Laboratories. A number
of EPA and outside experts have reviewed earlier drafts of the
document, and their comments are reflected in this final. version.
This document should not be confused with the reports on
encapsulants prepared by Battelle Columbus Laboratories: their
purpose is to evaluate specific commercially available products,
while this document is intended to provide general guidance on
when and how to encapsulate asbestos-containing material.
The guidelines in this document for deciding whether
encapsulation is advisable and for determining what encapsulant
to use are based on the best technology presently available, but
adherence to the guidelines will not necessarily insure that the
proper decisions will be made. Similarly, although the
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V
T
guidelines for application of encapsulants in Chapter Five are
based on the best currently available technology, and are
designed to reduce building contamination and exposure of workers
to asbestos, adherence to them will not necessarily guarantee a
risk-free procedure for asbestos encapsulation.
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CHAPTER ONE:
ADVANTAGES AND DISADVANTAGES
OF THE USE OF ENCAPSULANTS
Encapsulation can solve some asbestos exposure problems easily
and adequately. In other situations/ however, encapsulation is
definitely not advisable, and attempts to use encapsulants in
these situations may lead to greater exposure problems than would
have occurred if nothing had been done.
Encapsulation is often advisable in situations where the
asbestos-containing material is virtually impossible to remove.
For example, asbestos was often spray-applied to extremely
'complex surfaces, sucu au ^x^ auu uucc woe*, oc ceilings with
numerous surface irregularities. Since it would be very
difficult to remove asbestos from such complex surfaces,
encapsulation may be a good solution. The use of encapsulants is
often also advisable on denser, harder materials (called
"trowelled-on" or "cementitious") which contain asbestos.
Although cementitious materials typically do not present exposure
problems as severe as those caused by fluffy or spongy asbestos-
containing materials, it may be advisable to encapsulate them as
a precaution against future deterioration and damage.
However, encapsulation is not always advisable even in these
situations. Often it is not as easy and inexpensive as it may
appear at first. Further, using an encapsulant on asbestos-
containing fireproofing material may affect the material's
fireproofing ability, causing problems with the building's fire
rating and fire insurance. Encapsulating asbestos-containing
material may also make it difficult to remove the material later
in compliance with EPA regulations (see below, pages 5-6).
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Aside from these general problems, encapsulation has a number of
specific limitations as well; because of these limitations, it is
rarely a suitable approach to asbestos exposure problems if the
problems are severe. If asbestos-containing material has poor
cohesive strength, or has been damaged by water, or is not firmly
attached to the underlying surface, or is accessible to the users
of the building, then encapsulation is not a suitable approach.
Encapsulation is also not advisable on friable materials.
Friaole materials have poor cohesive strength; they can be pulled
apart easily with the hands, or crushed or reduced to powder by
hand pressure.* Fluffy, spongy asbestos-containing materials are
often highly friable; if they are, they should not be
encapsulated (see below, page 6).
Given all these variables, the performance of an encapsulant on a
particular piece of asbestos-containing material is
unpredictable. The problem is complicated by the fact that a
given encapsulant may perform very differently when applied to
two different types of material. It may perform extremely well
on one material and fail completely on another. For this reason,
EPA strongly recommends that any encapsulant be tested in the
field on the actual material before a final decision to use it is
made (see Chapter Five, page 30).
The remainder of this chapter discusses some of the advantages
and disadvantages of the use of encapsulants. Each of these
should be considered carefully before any decision is made to
encapsulate.
See Asbestos-Containing Materials in School Buildings; A
.Guidance Document,Part 1,pages 3 and 13,for a more
detailed discussion of friability.
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Advantages of Encapsulation
1. Encapsulation can control asbestos exposure problems
without necessitating the removal of the asbestos-
containing material.
Encapsulation may be a practical means of preventing the release
of asbestos fibers into the air and reducing the building users'
exposure to asbestos. Since it should make the removal of the
asbestos-containing material unnecessary, encapsulation retains
most of the advantages of having the material in the building.
Encapsulation avoids the expense and additional time required to
replace the asbestos-containing material, which is often
necessary after removal jobs.
2. Encapsulation is usually the quickest method of
control.
Encapsulation is a considerably less complicated task than
removal or the construction of barrier systems. Removal, in
.particular, is likely to be a more involved and time-consuming
process, especially since the asbestos-containing material must
often be replaced with a similar, but asbestos-free, product
(fiber glass or cellulose, for example).
However, this difference in time requirements is not as great as
it may appear at first glance, since certain measures to protect
the workers and to prevent contamination of the outside air are
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necessary during any corrective action (removal, enclosure, or
encapsulation). These measures add to the time required for any
of tnese techniques.*
3. Encapsulation is usually the least expensive control
method in the short run.
Since encapsulation is a simpler process than removal, it is
usually less expensive. Prices for any sort of asbestos control
vary widely, depending on local wage rates, the type and location
of the surface area, and the materials which are used.
One should bear in mind that the real cost of any asbestos
control technique is likely to be greater than it first appears,
because factors other than the basic cost of the job must be
included. For example, the costs of periodic inspection for
damage and aging should be included in an economic analysis of
encapsulation. The long-term costs of using encapsulants may
also include periodic recoating, a consideration which may make
encapsulation much more expensive than it looks at first.
4. Encapsulation is often a good control method for
cementitious asbestos-containing material.
Cementitious materials are usually composed of asbestos and other
materials (e.g., vermiculite and perlite), mixed with cement.
They are dense and usually fairly hard, and have a coarse,
textured appearance. Although they can be damaged by hand, they
are not fluffy or spongy. They are less than 3/4 inch thick
The protective measures are discussed in Chapter Five of this
document, in Asbestos-Containing Materials in School
Buildings; A Guidance Document,, and in Guidelines for
Removal of Friable Asbestos-Containing Material.
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(usually 1/8 inch to 1/2 inch) and usually contain less than 15%
asbestos. Cementitious materials can deteriorate with age and
can be friable, but in general they do not present exposure
problems as severe as those caused by fluffier materials because
their asbestos content and friability tend to be lower.
For cementitious materials in good condition, encapsulation is
often a good solution because it can help to control future
release of fibers easily and inexpensively. However, if
cementitious material is water damaged or accessible to the
building's users, or if it is not firmly adhering to the
substrate, it should not be encapsulated (se.e below).
Disadvantages of Encapsulation
1. The asbestos source remains in the building.
Encapsulation controls the release of fibers from asbestos-
containing material, but it does not provide a lasting solution
since the asbestos remains in the building. For this reason, the
encapsulated material must be checked periodically to ensure that
the encapsulant coat has not been damaged. Whenever the building
is renovated, or whenever repair work is conducted near the
material, the workers must be careful not to damage the sealed
asbestos-containing material. It also appears that encapsulants,
once applied, will deteriorate over time, and that the need for
recoating will recur periodically throughout the life of the
building.
2. Encapsulated material may be difficult to remove in
compliance with EPA regulations.
When the building is eventually demolished, or when the asbestos-
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containing material has to be removed, another serious problem
may occur. Under EPA regulations, before any building containing
friable asbestos-containing material is demolished or before any
friable asbestos-containing material is removed from a building,
the material must be wetted down (to prevent the release of
asbestos fibers into the environment), removed separately, and
buried.
Since encapsulants generally form a water-tight barrier, their
use makes subsequent wetting of the asbestos-containing material
difficult at best. Encapsulation may therefore make it difficult
to comply with EPA regulations during later removal or demolition
projects.
3. Encapsulation is not suitable for asbestos-containing
material which has poor cohesive or adhesive strength.
Encapsulation should not be considered on any asbestos-containing
material with poor cohesive strength. Some material with poor
cohesive strength is friable, that is, it can be crushed or
reduced to powder in the hand. Even if material is not friable,
it may have poor cohesive strength: an example is material which
is separating from itself in layers. If materials with poor
cohesive strength are encapsulated, the weight of the encapsulant
may cause them to deteriorate or delaminate even faster.
Similarly, encapsulants should not be applied to asbestos-
containing material which has poor adhesive bonding to the
substrate. The substrate is the underlying surface (for example,
concrete or structural steel) to which the asbestos-containing
material has been applied. If an encapsulant is applied to
materials with poor ashesion to the substrate, the additional
weight of the encapsulant may cause the material to separate
completely from the substrate and fall.
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i-'-'s-'''.« % *»*""ci ?i ^
A simple test which has been used widely to determine whether
asbestos-containing material has sufficient cohesive and adhesive
strength to sustain the weight of an encapsulant is described in
.Appendix B (page 37).
4. Encapsulation is not suitable for water damaged
materials.
In any case where the asbestos-containing material has been
damaged by water from roof or plumbing leaks, or where such
damage mignt occur/ encapsulants should not De used, water
leaking through asbestos-containing material will dissolve some
of the binders that hold it together and to the substrate. This
means that water damaged materials tend to have poor adhesive and
cohesive strength, and encapsulants are not appropriate for such
materials.
In addition, if areas subject to water damage are encapsulated,
water may be trapped in the material behind the encapsulant,
dissolving still more of the binding agent. Eventually the
combined weight of the encapsulant and the trapped water may
cause the asbestos-containing material to fall, taking the
encapsulant
layer with it and releasing asbestos fibers into the surrounding
air.
If the source of the water damage is repaired and the damaged
material is selectively removed and replaced, encapsulation may
be considered if the other conditions outlined in this chapter
are met.
5. Encapsulation is not suitable for materials which are
accessible to the users of the building.
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Encapsulants are designed to withstand some impact and
abrasion. However, EPA knows of no encapsulant which can
withstand repeated impact, and if encapsulated material is
damaged by accident or vandalism asbestos fibers may be
released. This problem is one of the major limitations of the
usefulness of encapsulants.
Because of this limitation, encapsulation should not be
considered on asbestos-containing materials which are accessible
to, or routinely disturbed by, the building's users. Surfaces
which are less than about ten feet from the floor or are
routinely disturoea curing maintenance, as wen as surraces sucn
as the ceilings of gymnasiums (which can be damaged by balls and
other objects), should not be encapsulated.
6. Encapsulation is not advisable for asbestos-containing
materials more than one inch thick.
Encapsulation also should not be considered on asbestos-
containing materials which are more than an inch thick. Tests
have indicated that even the best penetrating encapsulants, which
are designed to saturate asbestos-containing material and bind it
together and to the substrate, cannot completely penetrate
material which is more than one inch thick.* Users of
encapsulants should not expect penetration of greater than one
inch; therefore, encapsulants cannot be expected to improve the
adhesion of a thicker material to the underlying surface. The
weight added to the material by any bridging or penetrating
encapsulant may cause a failure of the material's cohesive or
adhesive strength. The exception to this rule is asbestos-
The tests are described in Evaluation of Sealants for
Sprayed-On Asbestos-Containing Materials in Buildings (see
Introduction).
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contain-ing material insulation material on pipes and ducts, which
may be suitable for encapsulation even if it is more than one
inch thick.
7. Encapsulation is not advisable in buildings and rooms
which are subject to vibration.
Vibration appears to possess the ability to shake spray-applied
asDestos-containing material from the substrate even if the
material has been encapsulated. In buildings and rooms which are
subject to high vibration, encapsulation is not recommended.
This problem is most serious in airports, in buildings near
heavily travelled roadways or railroads, and in rooms with heavy
machinery or fans. However, EPA also recommends strongly that
asbestos-containing materials in rooms beneath gymnasiums and
other high-activity areas not be encapsulated.
8. Encapsulation of asbestos-containing fireproofing
material may reduce the fireproof ing qualities of the
material.
Asbestos-containing material often functions in buildings as
fireproofing. If it is encapsulated, its fireproofing qualities
may be impaired. This, in turn, may affect the fire rating of
the building.
EPA is currently conducting further research into this aspect of
encapsulation. Although it does not preclude consideration of
the use of encapsulants, building owners may wish to consider
this factor before making a decision to encapsulate.
9. Encapsulation may reduce or destroy the acoustical
properties of the asbestos-containing material.
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Asbestos-containing materials were often applied for acoustical
insulation. If an encapsulant is applied to asbestos-containing
material, the ability of the material to deaden sound tends to be
diminished.
However, tnis factor does not, by itself, preclude the
possibility that encapsulation is feasible. The other techniques
for controlling asbestos exposure also have detrimental effects
on the acoustical properties of asbestos-containing materials.
Enclosure may also reduce the acoustical properties of the
material. If asbestos-containing material is removed, it often
must be replaced by an environmentally acceptable substance witn
similar acoustical qualities, such as fiber glass or cellulose.
In summary, encapsulation can be a practical method to control
the release of asbestos fibers, but certain limitations make it
useful only in a relatively small number of cases. Where
asbestos-containing material is accessible to the users of the
building, has poor cohesive or adhesive strength, is water
damaged, or is more than an inch thick, encapsulation is not
recommended. Encapsulation is also not recommended on friable
materials. EPA estimates that encapsulation is an appropriate
control technique in no more than 10% to 15% of all cases where
asbestos-containing material requires corrective action.
The following chart combines most of the information presented in
this chapter in a simple format designed to help building owners
and school administrators decide whether encapsulation is
appropriate in their buildings. It is designed only to
supplement the discussion and should not be used by itself.
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TABLE 1
APPROPRIATE SITUATIONS FOR ENCAPSULATION
Does the material have
poor cohesive strength?
Yes
Does the material adhere poorly
to the underlying surface?
Yes
Has the material been damaged by
water, or is there reason to
believe that water damage might
occur?
Yes
Is the material accessible
to users of the building?
Yes
No
Does the material cover
pipes or duct work?
\
Yes
Is the material less
than one inch thick?
No
Yes
Is the material subject
to high vibration?
Yes
NO
Encapsulation is NOT
a suitable approach.
Encapsulation is an
alternative.
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CHAPTER TWO:
THE CHOICE BETWEEN BRIDGING AND PENETRATING ENCAPSULANTS
If the decision to encapsulate has already been made, the next
question is whether to use a bridging or a penetrating
encapsulant. The purpose of a bridging encapsulant is to form a
tough membrane over the surface of the asbestos-containing
material which should prevent the release of asbestos fibers. A
penetrating encapsulant is designed to saturate the material and,
as it dries, to Dind the asbestos fibers to one another and to
tne other substances in the material.
Penetrating encapsulants, in general, have lower viscosities than
oriaging encapsulants. This means that they are thinner and flow
more easily. Viscosity is measured in centipoises; water, for
instance, has a viscosity of one centipoise. Penetrating
encapsulants usually have viscosities up to one hundred
centipoises, while many bridging encapsulants are so thick that
their viscosity is measured in thousands of centipoises.
Penetrating encapsulants usually also have a lower solid content
than bridging encapsulants.
Another difference between bridging and penetrating encapsulants
is that bridging encapsulants are almost always pigmented for
aesthetic purposes. On the other hand, almost no penetrating
encapsulants contain pigment because its presence would inhibit
their penetration. Dyes (not pigments) can be added to
penetrating encapsulants to color them (see Chapter Five, page
32) .
The choice of what kind of encapsulant to use often depends on
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tne characteristics of tine material which is to be
encapsulated. This chapter discusses a number of characteristics
of asbestos-containing material and shows how each affects the
choice between oridging and penetrating encapsulants.
Friaoility
As explained in Chapter One, material with high friability should
not be encapsulated. If, however, the decision has been made to
encapsulate asbestos-containing material which is moderately.
friaole and less than one inch thick, penetrating encapsulants
are preferable. Penetrating encapsulants are designed to reduce
the friaoility of the material by soaking into it, binding the
fibers together, and increasing the material's cohesive strength.
Because bridging encapsulants are not designed to penetrate into
the asbestos-containing material, they will not increase its
cohesive strength. The use of bridging encapsulants on friable
material may make the problem worse, because the weight of the
encapsulant may make the material delaminate even faster.
There are two exceptions to this point. One is discussed below
(page 16) in the section on the shape of the surface: for
friable asbestos-containing material on complex surfaces such as
pipes and ducts, a bridging encapsulant may actually be
preferable to a penetrating one. The second relates to
cementitious materials, which, even if they are somewhat friable,
may be treated with a bridging encapsulant (see page 16).
Water Damage
With regard to water damaged materials, there is no real
distinction between bridging and penetrating encapsulants. For
the reasons given in Chapter One, water damaged material should
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not be encapsulated.
Imperfect Adhesion to the Substrate
Asbestos-containing material which adheres imperfectly to the
substrate snould not ordinarily be encapsulated either with
bridging or with penetrating encapsulants, since the additional
weight of the encapsulant may cause the material to fall. If an
encapsulant penetrates all the way through the material to the
substrate and binds it to the substrate, this problem may be
avoided, but this will not often be the case.
Bridging encapsulants, which are not designed to penetrate
through the material, will obviously not improve the material's
adhesion to the underlying surface. Most penetrating
encapsulants penetrate less than an inch into spray-applied
asbestos material, and are unlikely to bind thicker asbestos-
containing materials to the substrate. If the material adheres
imperfectly to the substrate, it should be removed or enclosed
rather than encapsulated.
Accessibility
Most surfaces in any building are occasionally exposed to damage
from the building's users. On surfaces for which this exposure
occurs routinely, encapsulation is not recommended (see Chapter
One, pages 7-8). If, however, the decision is made to use an
encapsulant on a surface which is disturbed occasionally by
custodians and maintenance workers, a penetrating encapsulant is
probably preferable.
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Tests conducted for EPA indicate that penetrating encapsulants
are slightly more susceptible to damage from impact and abrasion
than bridging encapsulants. * However, -the consequences of
failure in the case of a bridging encapsulant are likely to be
more severe. The membrane created by a bridging encapsulant
covers/ but does not bind, the asbestos fibers behind it. If
this membrane is damaged, fibers can easily escape into the
air. Penetrating encapsulants, on the other hand, should
continue to hold the fibers in clumps, preventing their
widespread release into the air.
However, the use of a penetrating encapsulant is no guarantee of
success. If asbestos-containing material which has been treated
with a penetrating encapsulant is damaged, the clumps of fibers
falling to the floor may be ground underfoot and may eventually
bring about increased levels of exposure. Further, unless the
encapsulant has penetrated completely through the material,
unencapsulated material may be exposed when the encapsulant is
damaged. Hence, although penetrating encapsulants are preferable
to bridging encapsulants on material which will be exposed to
human contact, the best solution for material which is frequently
contacted is .removal or enclosure.
Acoustical Properties
Asbestos-containing material which serves as acoustical
insulation (e.g., in auditoriums and theaters) is likely not to
function as well after any encapsulant has been applied.
The tests are described in Evaluation of Sealants for
Sprayed-On Asbestos-Containing Materials in Buildings, a
report preparedfor EPA by Battelle Columbus Laboratories
It is available from EPA's Industry Assistance Office
(call 800-424-9065; in Washington B.C., 554-1404).
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Sprayed-on material adsorbs sound because of its dead air spaces
and because of its irregular surface. Penetrating encapsulants
reduce tiie dead air space, while bridging encapsulants create a
smooth layer on the surface. Either will impair the material's
acoustic properties to some extent.
Cementitious Materials
Cementitious materials are described in Chapter One, pages 4-5.
It is important to recognize the distinction between cementitious
materials, which are dense and relatively hard, and fluffy,
spongy asbestos-containing materials. Altnougn Doth may
deteriorate with age and either may be friable, cementitious
materials typically present less severe exposure problems because
of their thinness, lower susceptibility to damage, and generally
low asbestos content.
For cementitious materials, a bridging encapsulant is preferable
to a penetrating encapsulant. A bridging encapsulant should
effectively prevent the release of fibers from cementitious
materials. If the material is hard, completely undamaged, and
inaccessible to building users, the use of a good quality latex
paint with a high rubber content may also provide adequate
protection against future fiber release (see Chapter Four, page
24).
The Shape of the Surface
Asbestos-containing material on a large, flat ceiling without
projecting beams or other irregularities is not well suited to a
bridging encapsulant, unless the material is cementitious and in
good condition. On complex surfaces involving numerous beams,
pipes, and ducts, however, a bridging encapsulant may well be
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preferable. It will wrap around the irregularities in the
surface, enveloping the material and Dinding it within the
continuous membrane of the encapsulant.
Surfaces Which Have Previously Been Encapsulated or Painted
Penetrating encapsulants are not suitable for use on material
wnich has already been encapsulated or painted. They cannot
penetrate the water-tight surface formed by the old coat of
encapsulant or paint/ and thus cannot function properly. Heavy
accumulation of dirt or soot on the surface of asbestos-
containing materials may also prevent the penetration of
encapsulants.
When recoating a surface that was previously encapsulated with
either a penetrating or a bridging encapsulant, a bridging
encapsulant should be used. It is important to choose an
encapsulant which can adhere to the older encapsulant layer: for
example, if a butyl rubber bridging encapsulant was used in the
first place, it is probably advisable to recoat it with a similar
product. Note that material which is poorly attached to the
substrate should not be encapsulated, even if it has previously
been painted.
For material which has previously been treated with latex paint,
it may be advisable to recoat it with a good quality, high rubber
paint (see Chapter Four).
A table summarizing the differences between bridging and
penetrating encapsulants appears on the next page. It is
designed to supplement the discussion in this chapter and should
not be used by itself.
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TABLE 2
COMPARISON OF BRIDGING AND PENETRATING ENCAPSQLANTS
Bridging Penetrating
encapsulant encapsulant
Improves cohesive strength
of material (i.e., reduces
friability)?
no
yes
Appropriate for material which
adheres poorly to substrate?
no
no
Appropriate for water-damaged
material?
no
no
Allows fiber release readily
yes
sometimes
(see page 15)
Impairs acoustic insulating
properties of material?
yes
yes
Preferable for material on
pipes and ducts?
yes
no
Preferable for cementitious
material?
yes
no
Appropriate for material which
has already been painted or
encapsulated?
yes
no
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CHAPTER THREE:
CHOOSING THE RIGHT ENCAPSULANT
The field of asbestos encapsulation is a new one, and both
contractors and building owners suffer from a lack of hard
information about how different encapsulants compare with one
anotner. This chapter offers general guidelines to help
contractors and building owners choose an encapsulant.
The best way to choose an encapsulant is to field test several
encapsulants on the material to be encapsulated. When possible,
field trials should be performed prior to the final selection of
an encapsulant. The information in this chapter, combined with
the knowledge gained from field tests, should insure that a
proper encapsulant is selected.
This chapter does not contain information on specific products.
For information on currently available encapsulants, please
contact the Regional Asbestos Coordinators (see Appendix A).
The American Society for Testing and Materials (ASTM) is writing
standards by which encapsulants can be judged. ASTM plans to
publish these standards at some time in 1981.*
This chapter is based on early -versions of the 'ASTM standards.
It discusses a number of characteristics of encapsulants which
one should consider carefully before choosing a specific
For more information, contact ASTM at 1916 Race Street,
Philadelphia, Pennsylvania 19103.
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product. These general characteristics can oe used witn
Battelle's information on specific products to choose the best
encapsulant for a particular job. The first three
characteristics are especially important: they are toxicity,
flammability/ and method of application.
Toxicity
An encapsulant should not release toxic substances into the air
wnen it is applied. Solvent-based encapsulants, or encapsulants
for whicn the vehicle (the liquid in which the solid parts of the
encapsulant are suspended) consists entirely of hydrocarbons, are
not recommended because their use may be dangerous to workers.
The rooms where encapsulants are applied should be isolated by
plastic barriers,* and if the encapsulant does release toxic
fumes in the enclosed space the workers could quickly be in
serious danger.
The encapsulant also should not release any toxic materials after
it is dry. Even if it burns, the encapsulant should not release
toxic gases or an undue amount of smoke.
For information on the toxic gas generation of encapsulants,
please consult the Battelle report, or write to the manufacturers
asking for their products' performances on tests described in the
National Bureau of Standards's Technical Notes 757 and 808.
Manufacturers should be willing to supply this information, since
this is an important .characteristic of any encapsulant.
See Asbestos-Containing Materials in School Buildings; A
Guidance Document, Part 1, pp. 20-25, as well as Guidelines
for Removal of Friable Asbestos-Containing Material,for
information on isolation of the work area.
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Flammability
The encapsulant, once applied, should not be flammable. This is
especially important because asbestos-containing material usually
serves as a fire retardant in buildings; use of an encapsulant
which impairs these fire retardant properties may endanger the
lives of the building's users.
Encapsulant manufacturers generally run tests on their products
to insure that they will not increase the flammability of the
encapsulated material. By consulting Battelle's report, or by
writing to manufacturers and asking for the results for their
products or ASTM Standard Test t; 10^, contrctccucb ciuu uu.Lj.uiuy
owners can get an idea of how encapsulants compare. EPA
recommends strongly that encapsulants be used which have Class
"A" fire ratings based on this test.
Method of Application
The use of a roller or brush on friable asbestos-containing
materials is very likely to lead to dangerous fiber release.
Encapsulants must be applicable by spray equipment.
Encapsulants which must be applied by air spray equipment strike
the asbestos-containing material at greater pressure than those
applied by airless spray, and therefore are more likely to
dislodge asbestos fibers from the surface of the material.
Encapsulants which can be applied by airless spray equipment are
therefore preferable to those which must be applied by air
spray.
Other Qualities
There are six other characteristics described by Battelle or ASTM
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as desirable properties of encapsulants. The first four are
essential, while the last two are less critical. Each is
discussed briefly below.
1. The encapsulant should either penetrate into the material and
bind the fibers together,'or form a tough membrane over the
surface of the material. These qualities are discussed in
detail in Chapters One and Two, and should be considered
essential.
2. The encapsulant should be able to withstand some abuse
without allowing the release of any fibers, particularly in
cases where the asbestos-containing material is likely to be
occasionally disturoea.
3. The encapsulant should be water insoluble when cured.
4. The encapsulant should still have sufficient integrity, after
a minimum of six years, to allow recoating. In other words,
it should be fairly durable.
5. The encapsulant should not destroy the acoustical properties
of the asbestos-containing material. This quality is
obviously more important in some cases than in others, and
any encapsulant will probably impair the acoustical
properties of the encapsulated material to some extent (see
above, pages 9-10 and 15-16). Building owners who plan to
encapsulate auditoriums or theaters may wish to contact an
acoustical consultant or acoustical engineer.
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6. The encapsulant should allow for topcoating by conventional
paints where this is required £or aesthetic reasons. This
quality, again, will be more important in some cases than in
others.
These guidelines, used in conjunction with the information
available from the Regional Asbestos Coordinators, should help
contractors and Duilding owners select an acceptaole
encapsulant. However, the best way to tell whether an
encapsulant will perform on a given surface is to field test, it
by applying it to a small section of the surface (see page 30).
EPA recommends that several encapsulants be field tested in this
manner before a final decision is made regarding which one to
use.
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CHAPTER FOUR:
LATEX PAINTS:
FOR USE ONLY ON CEMENTITIOUS MATERIALS
The application of latex paint as a control technique for any
asbestos-containing material which is fibrous/ fluffy, spongy, or
highly friable is not recommended. Latex paints are not designed
to encapsulate such materials and cannot be expected to do so
effectively. Latex paints should be considered for use only on
undamaged cementitious materials, such as acoustical plasters.
The major component of a cementitious, acoustical plaster is
usually a dense, non-fibrous mixture of granular material. The
only fibrous component is the asbestos, usually at a
concentration of less than 15%. This material has a coarse sand,
textured appearance and is most often 1/8 inch to 1/2 inch thick,
with a maximum thickness of 3/4 inch. Such materials are friable
if they are soft and can easily be indented by hand pressure, and
if a powder residue remains on the hand when the material is
rubbed.
If asbestos-containing material is unsuitable for encapsulation,
it is not suitable for application of latex paint either. The
limitations of latex paint are even more acute than those of
encapsulants, so latex paint should not be applied to any
asbestos-containing material which is water damaged, accessible
to the building's users, more than 3/4 inch thick, or adhering
poorly to the substrate.
Cementitious material may be considered for treatment with latex
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paint if the material is in good condition, has not been damaged
by water/* and is not easily accessible. For cementitious
asbestos-containing materials which have previously been covered
witn latex paint, a coat of good quality latex paint with a high
rubber content may b.e the most effective treatment because it is
most lixely to adhere to the older layer of paint.
Although research on the use of latex paint to encapsulate
cementitious asbestos-containing materials has been very limited,
the following guidelines are offered to aid in the selection of
an appropriate latex paint.
Two major components in latex paint are the pigment and the
vehicle (the vehicle is the liquid in which the pigment is
suspended; it contains mainly water). The label should show the
percentage, by weight, of pigment and vehicle. Often the vehicle
percentage is subdivided into percent water and percent vehicle
resin solids or vehicle binder solids.
Good quality latex paint has a 60% or more vehicle content with a
high percentage of vehicle resin solids: of the vehicle, at
least 25% should be vehicle resin solids. If the percentage of
vehicle resin solids is not stated on the label, it can be
determined by subtracting the percent pigment from the percent
total solids. In general, the higher the percentage of vehicle
resin solids, the more durable and more flexible the coat of
paint will be. If the latex paint does not have a high
percentage of vehicle resin solids, it may be inflexible and
become brittle or crack with age. Accidental disturbance of the
coating by building users, or uneven settling of the building,
If the cementitious material has small, isolated water
damaged areas, treatment with latex paint may be considered
if the source of the water damage is repaired and the damaged
material is removed and replaced. This applies only if the
material is otherwise in good condition and is not accessible
to building users.
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may easily crack or otherwise damage inflexible latex membranes,
allowing the release of asbestos fibers.
The application rate of latex paint should be 75 to 100 square
feet per gallon. This application rate should result in a
mambrane with a dry film thickness grater than 4 mils
(0.004 inch). An airless spray gun should be used to apply the
paint. EPA recommends that the cementitious material first be
sprayed with a light mist coat with the gun held 18" to 24" away
from the material. This light mist coat should seal loose fibers
into'the surface and prevent the cementitious material to
continue to soak up the latex paint rather than build a
membrane. Once this has been allowed to dry completely, a
thicker coat can be added; this two-step application is
considered to be the first coat.
Wait until each coat dries .before adding another one. Each
subsequent coat should be applied at a 90 degree angle to the
direction of the preceding coat application. This application
technique should prevent any holes or voids from being formed in
the membrane and should assure complete coverage of the
cementitious material.
Note that, in the application of latex paint, all precautions
described in Chapter Five should be followed, just as though an
encapsulant was being applied.
Once again, the use of latex paints should be considered only on
cementitious material in good condition. For any spongy or
fluffy material containing asbestos, the use of latex paints is
not recommended.
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CHAPTER FIVE:
ENCAPSULANT APPLICATION
The importance of proper application of an encapsulant cannot be
overstressed. The quality of the contractors' work will not only
determine the effectiveness of the encapsulation, but may also
'affect the health of the workers themselves. Many failures of
encapsulated materials ar'e due to poor application rather than
the quality of the encapsulant or the material that was
encapsulated. No encapsulant, if improperly applied, can prevent
the release of asbestos fibers; careless procedures can easily
expose workers and the building users to asbestos, as well as
involving additional costs to correct the problems caused by the
failure of the application. For these reasons, all contractors
wno are preparing to encapsulate asbestos-containing materials,
and all administrators who are writing contract documents, should
read this chapter carefully.
Applicable Regulations and Further Information
The Occupational Health and Safety Administration (OSHA)
regulates workplace practices and the levels of airborne asbestos
to which workers may be exposed. EPA also has issued regulations
which govern emissions from asbestos work and asbestos disposal,
and has developed general recommendations for use in preparing
encapsulation contracts. If the recommendations are used in
preparing contract documents, and if the contract specifications
are strictly enforced, workers and users of the building will be
protected from undue exposure to asbestos.
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Asbestos-Containing Materials in School Buildings; A Guidance
Document contains the complete text of the OSHA and EPA
regulations governing encapsulation work as well as sample
specifications for encapsulation contracts. Guidelines for
Removal of Friable Asbestos-Containing Material also contains
information on proper work area set-up, worker protection, and
work practices (see Introduction for more information on these
documents).
Materials and Equipment
Encapsulation requires not only all materials standard tor indoor
paint application but a number of others as well. Respirators
and disposable clothing for workers, as well as scalable,
impermeable containers for the disposal of asbestos-contaminated
waste, are required by OSHA regulations. Plastic sheeting and
duct tape to seal off the work area, and portable shower
facilities for worker decontamination, are recommended by EPA.
Contractors desiring more information on materials should contact
their Regional Asbestos Coordinators, or consult the EPA
documents cited in the Introduction.
EPA recommends that encapsulants be applied to the asbestos-
containing material with airless spray equipment. Although the
use of an airless gun does not completely eliminate the
dislodging of asbestos fibers during the encapsulation job, this
release is substantially less than is the_case with conventional
air spray equipment.
Worker Training
EPA strongly recommends that all workers be thoroughly educated
in a number of subjects related to encapsulation before they
begin work. These subjects include the use and maintenance of
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respirators, the use of protective clothing, proper safety
procedures, personal decontamination procedures, techniques to
control fiber release in the work area, and proper application
procedures. OSHA requires that each employer establish a program
to train workers in the care and use of respirators and to ensure
proper storage of respirators when they are not in use.
Construction of Decontamination Area and Preparation of Work Area
Before encapsulation work begins, a decontamination area should
be constructed and the work area should be sealed off from the
rest of the building. These procedures are discussed in
consiaeraoxe aetau. in Aspestos-containing Materials in acnool
Buildings; A Guidance Document and in Guidelines for Removal of
Friable Asbestos-Containing Material, so they are not treated
extensively here.
Briefly, the procedures involve the construction of a clean room
and a contaminated equipment room with a shower between them, and
with airlocks consisting of plastic curtains to prevent the
escape of fibers into the outside air. The work area should be
completely isolated from the. rest of the building with barriers
constructed from 4- to 6-mil polyethylene sheets, and floors and
walls in the work area should be covered with polyethylene sheets
as well.
Work Practices and Personal Decontamination Procedures
These topics, too, are covered extensively by Asbestos-Containing
Materials in School Buildings; A Guidance Document and in
Guidelines for Removal of Friable Asbestos-Containing Material.
Contractors and specification writers should consult these
documents. Any person entering the work area must wear a
suitable respirator and disposable clothing. No clothing which
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will be worn in the street can be worn in the work area. The
same also applies to shoes: if shoes are worn in the work area,
they must be left in the contaminated room at the end of each
work shift.
No one may remove his or her respirator while in the work area.
Whenever leaving the work area, workers must remove their
contaminated disposable clothing and, in the shower, saturate
themselves and their respirators thoroughly before removing their
respirators. They should clean themselves and their respirators
thoroughly before changing into their street clothing.
Compliance with these specifications is'necessary to protect the
health of the workers and prevent contamination of the outside
environment.
Field Testing of Encapsulants
EPA recommends that the contractor and building owner arrange to
field test several encapsulants before a final decision is made
as to which to use. This will not only insure that the
encapsulant which is used is suitable for the material, but will
also enable the contractor to gain first-hand experience in
applying the particular encapsulant to the particular surface.
C .
After the work area has been isolated with polyethylene from the
rest of the building, field test the encapsulants by applying
each to a small area of surface. The contractor should use the
techniques and procedures he expects to use on the surface area
as a whole, and observe the results to see which encapsulant will
do the best job. He can also experiment with different drying
times, pressure settings, and so forth, and select the best
techniques when he begins the application of the encapsulant
selected. In testing an encapsulant in the field, the building
owner should check that the encapsulant cures to a durable finish
in a resonable time and that it adheres firmly to the asbestos-
containing material. He should also take a small core sample
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from the test patch to check the thickness of the coating (for a
building encapsulant or thickness of penetration (for a
penetrating encapsulant) .
Application of Encapsulant
The pressure of airless spray equipment is adjustable. The
correct nozzle pressure varies from 400 to 1500 pounds per square
inch/ depending primarily on the encapsulant's viscosity and
secondarily on its solids content. In general/ the lower a
substance's viscosity and percentage of solids, the lower the
pressures at which it can be sprayed. Since higher pressures
cause more asbestos fibers to be blown away from the surface, the
equipment should be set at the lowest operable pressure.
A second factor that affects application is the size of the tip
of the airless spray gun. Like pressure settings/ tip sizes
should be selected on the basis of the viscosity and percent
solids of an encapsulant. One way to test for proper tip size is
to spray the encapsulant briefly onto a surface from about 12
inches away. An appropriately sized tip will spray the
encapsulant in a fan approximately eight inches wide; it will
also distribute the encapsulant uniformly within the fan. An
improper tip will often concentrate the encapsulant at the fan's
edges.
Particularly on more friable material, it is usually a good
practice to apply first a light mist coat of the encapsulant.
The purpose of this preliminary coat is to moisten and seal loose
fibers and keep them from breaking away from the surface. This
mist coat should be applied in three or four quick passes with
the gun held 18 to 24 inches from the surface.
After an area of 16 to 20 square feet has been given the mist
coat, the applicator can proceed immediately to apply a heavier
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coating of the encapsulant, using eight or ten passes with the
gun held 10 to 12 inches from the material. The gun should be
kept in constant motion to create a smooth and even coat.
This two-step application is considered to be the first coat.
Most encapsulants should be applied in two or three separate
coats, with time allowed after each coat for the encapsulant to
cure. Note that the amount of drying time varies from
encapsulant to encapsulant, and that manufacturers'
recommendations should be followed. In general, penetrating
encapsulants should be allowed to cure for only about four hours
before the second coat is applied; if the first coat cures
completely, it will not allow the second coat to penetrate into
the material. Bridging encapsulants should be allowed to cure
for somewhat longer before another coat is added. Each
subsequent coat should be applied at a 90 degree angle to the
direction of the preceding coat application, to assure complete
coverage of the asbestos-containing material.
It is important not to apply too much encapsulant in each coat.
A penetrating encapsulant, if applied too thickly, can block the
surface of the material as it cures, preventing any subsequent
coats from penetrating into the material. Further, over-
application of a penetrating encapsulant can cause the asbestos-
containing material to become too wet and to break loose from the
substrate. This second problem is also important for bridging
encapsulants.
One method for preventing over-application is for the sprayer to
keep a mental note of the number of passes made with the spray
gun. An experienced applicator will also be able to tell by
listening to the sound the encapsulant makes when it hits the
surface: when the material becomes saturated, there will be a
distinct sound change. Third, the changing color of the material
as it is sealed can give an indication of how much encapsulant
constitutes a coat (if a penetrating encapsulant is unpigmented,
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food coloring or a similar dye—not a pigment— can be added to
give it a slight tint). Applying a different color encapsulant
for each coat will help to ensure complete covering.
Dilation also plays an important role in encapsulant
application. Some encapsulants must be diluted with water. Even
if dilution is not required, it often makes it possible to apply
the encapsulant at a lower pressure to reduce the release of
fibers. Dilution may also improve the penetrating quality of the
encapsulant. Most manufacturers give recommendations concerning
dilution on the labels of their encapsulants. Some
experimentation will also help determine when dilution is useful.
Most manufacturers will provide on request a data sheet including
recommendations for tip size, spray pressure, number of coats to
be applied, drying time, and so forth. Contractors and other
interested parties are strongly advised to obtain this
information.
Coverage
One-coat coverage rates for most penetrating encapsulants range
from 10 to 40 square feet of friable asbestos-containing material
per gallon of encapsulant. Bridging encapsulants may yield
slightly higher coverage, with one gallon providing one-coat
coverage of 20 to 40 square feet. These figures are based on
Battelle's studies of encapsulants, and tend to be lower than
manufacturers may claim.
The coverage rate of a penetrating encapsulant is dependent
primarily on the thickness of the material to be encapsulated and
the ability of the encapsulant to wet the material. The thicker
the material, the more encapsulant will be required to fill it
completely and penetrate to the substrate. Better penetrating
encapsulants often have lower coverage rates because they
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penetrate more deeply into the material.
Coverage with bridging encapsulants is also affected by such
variables as the degree of their penetration and tiie texture of
the surface. Unsurprisingly, the rate of coverage tends to be
lower on irregular surfaces.
High Humidity Areas
It is often difficult to encapsulate asbestos-containing material
in humid air, since the material may already be damp and thus
tend to absorb much less of the encapsulant than if encapsulation
were performed under dry conditions. This problem can be caused
by the humidity of the outside air or by conditions within a
building (e.g., the presence of an indoor swimming pool). To
avoid the first problem, encapsulation jobs should be undertaken,
as mucn as possible, on dry days. For the second problem,
measures can be taken to reduce the indoor humidity;
swimming pools can be drained and windows opened a few days
before the job begins to allow the material to dry out.
Asbestos Exposure Problems During Application of Encapsulants
Problems of worker exposure to asbestos during encapsulation jobs
can usually be attributed to failure to follow EPA and OSHA
regulations or guidelines: by attempting to encapsulate highly
friable material which should really be removed, by spraying
encapsulants at too high a pressure setting, or by holding the
spray gun too close to the surface. Any of these mistakes can
cause the encapsulant spray to dislodge pieces of asbestos-
containing material into the air, resulting in serious problems
of worker exposure to airborne asbestos. Failure to follow EPA
and OSHA regulations and guidelines could also result in total
faiure of the encapsulation.
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Exposure problems can also result from failure to observe EPA
recommendations for fiber containment during encapsulation
jobs. Consult Asbestos-Containing Materials in School
Buildings; A Guidance Document and Guidelines for Removal of
Friable Asbestos-Containing Material, and follow these
recommendations carefully. Failure to do so can result in
exposure of workers and building users to hazardous levels of
airborne asbestos, and may subject the responsible party to
punitive action by EPA or OSHA.
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APPENDIX A
Regional Asbestos Coordinators
Mr. Paul Heffernan
EPA Region I
Air & Hazardous Materials Div.
JFK Federal Bldg.
Boston, MA 02203
617-223-0585
CT, MA, ME, NH, RI, VT
Mr. Marcus Kantz
EPA Region II
Room 802
26 Federal Plaza
New York, N.Y. 10007
212-264-3059
Ms. Pauline Levin
EPA Region III (3SA-00)
Curtis Building
Sixth & Walnut Streets
Philadelphia, PA 19106
215-597-9359
DE, MD, PA/ VA, WV
Mr. Dwight Brown
EPA Region IV
345 Courtland Street
Atlanta, GA 30308
404-881-3864
AL, FL, GA, KY, MS, NC, SC, TN
Mr. Ibny Restaino
EPA Region V
230 S. Dearborn St.
Chicago, IL 60604
312-353-2291
IL, IN, MI, MN, OH, WI
Dr. Larry Thomas .
EPA Region VI
First Internat'l Bldg.
1201 Elm Street
Dallas, TX 75270
214-767-2734
AR, LA, NM, OK, TX
Mr. Wolfgang Brandner
EPA Region VII
324 East 11 Street
Room 1500
Kansas City, MO 64106
816-374-6538
NJ, NY, Puerto Rico, Virgin Islands IA, KS, MO, NE
Mr. Steve Farrow
EPA Region VIII
1860 Lincoln Street
Denver, CO 80295
303-837-3926
CO, MT, ND, SD, UT, WY
Mr. Kirby Narcisse
EPA Region IX
215 Fremont Street
San Francisco, CA 94105
415-556-3352
AZ, CA, HI, NV, Pacific Islands
Ms. Margo Partridge
EPA Region X
1200 Sixth Avenue
Seattle, WA 98101
206-442-5560
AK, ID, OR, WA
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APPENDIX B.
A TEST
WHICH INDICATES WHETHER FRIABLE ASBESTOS-CONTAINING MATERIAL
CAN SUSTAIN THE WEIGHT OF AN ENCAPSULANT
Introduction
This test, which has been adapted from the American Society for
Testing and Materials (ASTM) Standard Test Method E 736-80, has
been used extensively in some parts of the country.
Purpose
This test indicates whether friable asbestos-containing materials
have sufficient adhesive and cohesive strength to sustain the
weight of an encapsulant.
Materials
1. A cap, 3^4" m diameter and approximately ^2" deep. A hooK
shall be attached at the center.
2. An adhesive system of urethane resin to form a rigid foam,
3. A two pound weight.
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Method
1. Select at random three locations on the asbestos-containing
material on which to perform the test. Then, at each
location/ perform the following steps:
2. Mix a sufficient quantity of the urethane resin system in the
cap, and place the cap immediately placed against the friable
asbestos-containing material being tested.
3. Hold the cap in place until the resin has completely foamed
and has set sufficiently to become self supporting.
4. After the foam becomes hard, engage the weight carefully on
the hook. This applies a uniform force of 36 pounds per
square foot perpendicular to the surface.
5. The material must support the weight for one (1) minute at
each test location in order to pass the test.
Note: The adhered cap can be removed by carefully cutting the
foam away from the asbestos-containing material with a sharp
knife or hacksaw blade, or it can be left in place for future
tests.
Interpretation of Results
If friable asbestos-containing material does not pass this test,
encapsulation is probably not an appropriate method for
controlling fiber release.
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