Ventilation Checklist & Log
This checklist
discusses
eight major topic
areas:
Outdoor Air Intakes
System Cleanliness
Controls for Outdoor Air Supply
Air Distribution
Exhaust Systems
Quantity of Outdoor Air
Adequacy of Outdoor Air Supply
How to Measure Air Flow
Instructions:
1. Read the IAQ
Backgrounder.
2. Important! Read the
Ventilation Activity
explanations
accompanying this
checklist (pages 5-13).
3. Make one copy of the
Ventilation Log (pages 3-
4} for each ventilation
unit in your school.
4. Complete each activity
for each ventilation unit
and note the status of
each activity on the
Ventilation Log.
5. Return the Ventilation
Logs to the IAQ
Coordinator and keep
copies for future
reference.
Schools use a variety of methods for
ventilating the building with outdoor
air: 1) mechanically-based systems
such as unit ventilators, central HVAC
systems, and central exhaust systems,
and; 2) passive systems that rely on
operable windows, air leaks, wind, and
the stack effect (the tendency of warm
air to rise).
The majority of the Ventilation Check-
list/Log activities apply mainly to
mechanical ventilation systems, and
are designed to accomplish two
functions:
• Ensure that the ventilation system
is clean, and
• Ensure that an adequate amount of
outdoor air is supplied to occupied
areas.
Many of these activities should be
performed by individuals with appro-
priate training in mechanical systems
and safety procedures. Most activities
can be performed with basic mainte-
nance tools, but Activity 22 will
require airflow measurement equip-
ment that you may not have. The
section How to Measure Airflow, at the
back of this Checklist, describes the
type of equipment used to measure
airflow. The IAQ Coordinator has
information on how this equipment can
be obtained (Appendix C of the
Coordinator's Guide). Make an effort
to obtain this equipment before
conducting Activity 17. Supplying an
adequate amount of outdoor air to an
occupied area is necessary for good
indoor air quality, and measuring
airflow can only be done correctly with
equipment that can reliably tell you if
you're getting the proper amount of
outdoor air (visual inspection or feeling
for air movement is not sufficient).
Activities 17-21 can be applied to
passive ventilation systems. For
activities that do not apply, place a
"NA" in the date column of the Ventila-
tion Log.
Your school most likely has multiple
units and systems, so be sure to perform
the activities and complete the Ventila-
tion Log for each unit. The activities
are listed in a purposeful order to
prevent having to repeat activities for a
given unit as the inspection progresses.
The following is a recommended
process for saving time in performing
the activities:
Activities 1-3
Perform these activities for all outdoor
air intakes while outside the building,
and mark the results on the Ventilation
Log for each unit.
Activities 4-12
Perform these activities as a set on each
ventilation unit while you're in the
room and the unit is open. •
Activities 13-16
Perform these ventilation control
system activities as required by your
situation.
Activities 17-21
Perform these air distribution and
exhaust system activities as required by
your situation.
-------
Activities 22-23
Perform these activities regarding the
quantity of outdoor air on all units
while you have the airflow measure-
ment equipment available.
All of these activities are described in
the information following the Log. For
more detailed information see Building
Air Quality. A Guide for Building
Owners and Facility Managers (EPA-
400-1-91-033) listed in Appendix I of
theIAQ Coordinator's Guide.
Typical HVAC System
EXHAUST
AIR
OUTDOORS
RETURN AIR STAT
MIXED AIR STAT
FREEZE STAT
TEMPERATURE SENSOR
AIR CONTROL DAMPER
AIR FILTER®
CENTRAL AIR HAKDUNG UNIT
IMVEHTHATOR '—
-------
Name
School'
Room or Area
Ventilation Log
Instructions:
Q Make one copy of this Checklist and Log for each ventilation unit in your school.
Q Perform the activities on the Checklist and Log for each ventilation unit and record
your results.
Q One column is provided for each inspection. Put the date at the top of the column,
and initial each response. For subsequent inspections on the same unit, move to the
next column until the sheet is full.
Q A "No" response requires further attention.
ACTIVITY
NEEDS
ATTENTION
IF "NO"
DATE:
INITIALS
NEEDS
ATTENTION
IF "NO"
DATE
INITIALS
NEEDS DATE:
ATTENTION
IF "NO" i INITIALS
Outdoor Air Intakes (see page 5 for mote information)
1. Outdoor air intakes not obstructed
2. Outdoor air intake clear of nearby pollutant
sources
3. Outdoor air moving into intake
QYes
a NO
Q Yes
Q No
Q Y«
a NO
QY«
a NO
Q Yes
QNo
Q Yes
QNo
System Cleanliness (see page 6 for more information)
4. Filters in good condition, properly installed,
and no major air leaks
5. Drain pan clean and no standing water
6. Heating and cooling cofl(s) clean
7. Interior of air handling unit and ductwork
clean.
8. Mechanical room free of trash and chemicals
QYes
a NO
3 Ye.
a NO
Q Yes
a NO
QYes
a NO
QYes
Q No
Q Yes
a NO
a Yes
QNo
Q Yes
QNo
Q Yes
QNo
Q Yes
Q No
a YCS
Q No
1
Q Yes !
Q No
Q Yes
Q No
Q Yes
QNo :
Q Yes
QNo
Q Ye» i
QNo
Q Yes
QNo
Q Yes
Q NO
Controls for Outdoor Air Supply (see pages 7-9 for more information)
9. Controls information on hand
10. Clocks, timers, and switches properly set
11 . Pneumatic controls okay
12 Outdoor air damper operating properly
Q Yes
a NO
a Yes
a NO
a Yes
Q No
QY«
Q No
Q Yes
Q No
Q Yes
QNo
QYa
QNo
Q Yes
Q No
QY=
Q No
Q Yes
Qs-o
Q Yes
QNo
Q Y«.
Q No
-------
ACTIVITY
NEEDS
ATTENTION
IF'NO"
DATE:
INITIALS
NEEDS
ATTENTION
IF-NO-
DATE:
INITIALS
NEEDS
ATTENTION
IF •NO'
Controls for Outdoor Air Supply (continued)
13 FrectHBitieMt
1 4. Mixadakthamosattet properly
15. Ecooomiier set per specifications
1 6. Fans sopplyins outdoor air operate
eontxDiutsly timing occupied periods
a Yd
a NO
a NO
a Yd
a NO
QYes
QNo
a Yd
a NO
a Yes
a NO .
a YCS
QNo
a Yes
a NO
Air Distribution («*p«gcs9-10formore Information)
17>AlrdbtTibu£oQ fboction per design
1 1. AST Oow direciioa (relative pressures) okxy
a Yd
a NO
a NO
a Yd
a NO
a Yd
a NO
a YO
a NO
b Yes
a NO
a YO
a NO
a Yd
a NO
a Yd
a NO
a YCJ
QXo
Exhaust Systems (see pages 10-1 1 for more information)
tpoiuna
20. Local exhaust to($) remove enough sir to
2 1 . ExbBW ductwork setleS snd in good
condition
a Yd
a NO
a Yd
QYes
QNo
a Yd
a NO
a Yd
a Yes
a NO
a Yd
a NO
Q Yd
a Ye*
a NO
DATE:
INITIALS
'Quantity 'and Adequacy of Outdoor Air Supply (see pages 1 1-12 for more information)
22. Measure quantity of outdoor air
fl. fft£?V^f f3f pjfffdy
o. B*"'^1"'-^ of occspcos J^\"cd by BS tssc
c. CFMtocoafMna
(•.b)
23. RtcoremoxklioamTiitel (orlMs
tjrpeefBd:
a Yd
QNo
a Yd
a NO
'-
__„
— •
—
a Yd
a NO
-------
Explanatory Information for
Ventilation Log Items
OUTDOOR AIR INTAKES
If outdoor air intakes are deliberately blocked or become clogged with dirt or debris, areas they serve are likely to get insuffi-
cient outdoor air. Students or staff might experience stuffy or stagnant air, or develop health problems from exposure to accu-
mulated pollutants.
Q On a small floor plan (e.g., a fire escape floor plan), mark the locations of outdoor air intakes, based on mechanical plans
(if available) and your observations while performing these activities.
Q Obtain chemical smoke (or, alternatively, a small piece of tissue paper or light plastic) before performing Activity 3. For
more information on chemical smoke, see Haw to Measure Airflow, at the end of this Checklist.
Q Ensure that the ventilation system is on and operating in "occupied" mode
1. Ensure that outdoor air intakes are unobstructed
Q Check the intakes from outside the school building for .obstructions, such as debris, clogged screens, or make-shift covers
(e.g., boards or plastic)
Q Remove any obstructions
\ Q Install corrective devices if snowdrifts or leaves often block an intake
2. Ensure that outdoor air intakes are clear of nearby pollutant sources
Q Check the intakes from outside the school building to confirm that pollutant sources are not located near outdoor air intakes
• At ground level, look for dumpsters, loading docks, and bus-idling areas
• At roof level, look for plumbing vents, exhaust outlets (such as kitchen, toilet, or laboratory exhaust fans), puddles on the
roof, and mist from air-conditioning cooling towers
. Q Resolve problems due to pollutants near intakes
• Remove sources, where possible (for example, move a dumpster to another location)
• Separate the source from the intake (for example, add another pipe section to raise a nearby exhaust outlet above the intake)
• Change operating procedures (for example, turn off vehicles instead of idling at loading docks and bus stands)
3. Confirm that outdoor air is entering the system intake
Q Use chemical smoke (or, alternatively, a small piece of tissue paper or light plastic) to show whether air is moving into the
intake grille
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SYSTEM CLEANLINESS
Accumulated dirt can interfere with the proper operation of the ventilation system and lead to underventilation, uncomfortable
temperatures, less efficient operation (higher utility bills), more maintenance, and decreased life expectancy of equipment. Air
filters are intended primarily to prevent dirt and dust from accumulating in the HVAC system. If filters are not properly selected
and maintained, built-up dirt in coils and ducts could provide a habitat for microbiological growth. Filters that are clogged with
dirt restrict the flow of air through the HVAC system. If filters "blow out" and allow the passage of unfiltered air, dirt can
accumulate on coils (producing a need for more frequent cleaning) and reduce the efficiency of the heating and/or cooling
plant It is much less expensive to trap dirt with properly maintained niters than to remove it from ductwork, coils, fan blades,
and other HVAC system components.
WARNING: Do not clean dirty or biologically contaminated system components -when the system is operating and the building
is occupied.
WARNING: If there is visible biological growth, such as mold, minimize your exposure to air in the interior of ducts or other
HVAC equipment. Use proper respiratory-protection; obtain expert advice, about the kind of respiratory protection to use and
how to use it.
4. Inspect air filters on ventilation equipment . .
Q Install new filters as needed. Shut off ventilation system fans when replacing associated filters so that dirt will not blow
downstream. Vacuum the filter area before installing the new filter
Q Confirm that filters fit properly in their tracks, with no major air leaks that would allow air to bypass (flow around) the air
filter
Q Confirm that filters are installed in the proper direction for airflow
5. Ensure that condensate drain pans are clean and drain properly
• Drain pans should slant toward the drain so they do not collect and hold water
6. Ensure that heating and cooling coils are clean
7. Ensure that air handling unit(s) (air mixing chambers, coils, and fan blades) and duct interiors are clean
8. Ensure that the mechanical rooms are free of trash and chemicals .".'••• ....
Q Check mechanic^ rcxm for unsanitary conditions, leaks, or spills'
Q Confirm that mechanical rooms and air mixing chambers are not used to store trash or chemical products and supplies
-------
CONTROLS FOR OUTDOOR AIR SUPPLY
This group of activities is for ventilation systems that use fans or blowers to supply outdoor air to one or more rooms within a
: school. The primary objectives that you should keep in mind as you perform these activities are:
• Ensure that air. dampers are always at least partially open (minimum position) during occupied hours, and
• Ensure that the minimum position provides an adequate amount of outdoor air for the occupants.
These activities are fairly generic, and apply to most ventilation systems. See the figures in the IAQ Backgrounder for more
information.
Activities 9-11 generally serve multiple ventilation units, while activities 12-16 are related and performed at each individual
ventilation unit. Based on your equipment and experience, perform as many of the activities and make as many indicated repairs
as possible. Discuss the need for additional help for any uncompleted activities or repairs with your IAQ Coordinator.
9. Gather controls information
Your ventilation controls may be uniquely designed, and since there are many different types and brands of control components,
it can be very helpful if you:
• Gather and read any controls specifications, as-built mechanical drawings, and controls operations manual s that you may
have
• Contact the system installer or HVAC maintenance contractor to obtain controls information that is missing from your files
10. Check Clocks, Timers, and Seasonal Switches
Q Confirm that summer-winter switches are in the right position
Q Confirm that time clocks read the correct time
Q Confirm that time clock settings fit the actual schedule of building use (night/weekend set-back and set-up)
11. Check pneumatic control system components (if any)
Q Test the line.pressure at both the occupied (day) setting and the unoccupied (night) setting to determine whether the overall
system pressure is appropriate . •
Q Confirm that the line dryer is preventing moisture buildup
: Q Check the control system filters. The filter at the compressor inlet should be changed periodically in keeping with the
compressor manufacturer's recommendation (for example, when you blow down the tank)
Q Ensure that the line pressure at each thermostat and damper actuator is at the proper level (no leakage or obstructions)
Q Repair or replace defective components
-------
12. Check outdoor air damper operation
Before continuing, the air temperature in the indoor area(s) served by this outdoor air damper must be within the normal
operating range, and ensure that the outdoor air damper is visible for your inspection
Q Turn off the air handler connected to the outdoor air damper and confirm that the damper fully closes within a few minutes
Q Turn on the air handler and confirm that the outdoor air damper opens at least partially with little or no delay
Q Set the room thermostat as follows, and observe the damper for movement (damper should go to its minimum position, but
not completely closed):
• If in heating mode, set the room thermostat to 85°F
• If in cooling mode, set the room thermostat to 60°F, mark the current setting of the mixed air thermostat, and set it to a
low setting (about 45°F)
If the outdoor air damper does not move:
• Confirm that the damper actuator is linked to the damper shaft and that any linkage set screws or bolts are tight
• Confirm that rust or corrosion are not preventing free movement
• Confirm that either electrical wires or pneumatic tubing is connected to the damper actuator
• Reset thermostats) to appropriate temperature(s)
Proceed to Activities 13-16 if the damper seems properly operating
NOTE: The minimum damper setting, adjusted -with a nut or a knob, may have to be adjusted
to allow a larger damper opening if the amount of outdoor air supply measured in Activity 22
is not adequate for the number of occupants being served.
^^___^Zmiili_^___L___l^L_l lil_^_L!g^ in mi i
Unit Ventilators are sometimes specified to operate under one of the following ASHRAE sequences:
Cycle I: Except during warm-up stage (outdoor air damper closed), Cycle I supplies 100% outdoor air
at all times.
Cycle II: During the heating stage, Cycle II supplies a set minimum quantity of outdoor air. Outdoor
air is gradually increased, as required for cooling. During warm-up, the outdoor air damper, is closed.
(Typical sequence for northern climates.)
Cycle Hf: During the heating, ventilating and cooling stages, Cycle ffl supplies a variable amount of
outdoor air as required to maintain a fixed temperature (typically 55°F) entering the heating coil.
When heat is not required, this air is used for cooling. During warmup, the outdoor air damper is
closed. (Typical sequence for southern climates, with, adaptions for mechanical cooling.)
-------
The following four items may be responsible for keeping outdoor air dampers closed during the normal occupied cycle.
j - -.-.-•
13. Confirm freeze-stat condition
HVAC systems with water coils need protection from freezing. The freeze-stat may close the outdoor air damper and disconnect
the supply air when tripped. The typical trip range is 35°F to 42°F.
• If the freeze-stat has a manual reset button (usually red), depress the button. If a click is heard, the freeze-stat was probably
tripped. Consider replacing manual reset freeze-stats with automatic reset freeze-stats
• If the freeze-stat has an automatic reset, disconnect power to the controls and test for continuity across the terminals
14. Check mixed air thermostat
• The mixed air stat for heating mode should be set no higher than 65°F
• The mixed air stat for cooling mode should be set no lower than the room thermostat setting
15. Check air economizer setting
j
Economizers use varying amounts of cool outdoor air to assist with the cooling load of the room or rooms. There are two types
of economizers, dry-bulb and enthalpy. Dry-bulb economizers vary the amount of outdoor air based on outdoor air temperature,
and enthalpy economizers vary the amount of outdoor air based on outdoor air temperature and humidity level.
Q Confirm proper settings based on design specifications or local practices (dry-bulb setting typically 65°F or lower)
Q Check the sensor to make sure that it is shielded from direct sunlight .
16. Confirm that fans operate continuously during occupied periods
• Any fan that helps move air from outdoors to indoors must operate continuously during occupied hours, even though the
room thermostat is satisfied. .
• "If the fan shuts off when the thermostat is satisfied, change the control cycle to prevent underventilation.
AIR DISTRIBUTION
Even if enough outdoor air is brought into a school building,. IAQ problems can develop if the outdoor air is not properly
distributed. In such cases,, underventilatioh occurs in particular areas of the building 'rather than being widespread Problems
with au-distribution are most likely to occur in areas where: '
, • Ventilation equipment is malfunctioning
• Room layouts have been altered without adjusting the HVAC system
• The population of a room or zone has grown without adjustment to the HVAC system
• Air pressure differences move air contaminants from outdoors to indoors and transport them within buildings.
-------
In schools with mechanical ventilation equipment, fans are the dominant influence on pressure differences and air flows. In
schools without mechanical ventilation equipment, natural forces (wind and stack effect) primarily influence airflows.
To prevent infiltration of outdoor air and soil gas (e.g., radon), mechanically-ventilated buildings are often designed to maintain
a higher air pressure indoors than outdoors, which is known as positive pressurization (See "Exhaust Systems" and "How to
Measure Airflow" for a description of building pressurization). At the same time, exhaust fans control indoor contaminants by
keeping rooms such as smoking lounges, bathrooms, kitchens, and laboratories under negative pressure compared to surround-
ing rooms. "Negative pressure" and "positive pressure" describe pressure relationships. A room can operate under negative
pressure as compared to neighboring rooms, but at the same time it may be positive compared to outdoors.
17. Check air distribution
Verify that air pathways in the original ventilation system design continue to function.
Q Check to see whether operable windows have been replaced by windows that cannot be opened
D Check to see whether passive gravity relief ventilation systems and transfer grilles between rooms and corridors are func-
tioning. If they are closed off or blocked to meet modern fire codes, consult with a professional engineer for remedies
Q Verify that every occupied space has a supply of outdoor air (mechanical system or operable windows)
Q Confirm that supplies and returns are open and unblocked. If outlets have been blocked intentionally to correct drafts or
discomfort, investigate and correct the cause of the discomfort and reopen the vents
Q If you discovered areas with no source of outside air, modify the HVAC system to correct the problem
Q Check for barriers, such as room dividers, large free-standing blackboards or displays, or bookshelves, that could block
movement of air in the room, especially if they block air vents
18. Check air flow direction
Q Confirm that the system, including any exhaust fans, is operating on the occupied cycle when doing this activity
* Where outdoor contaminant sources have been identified, use chemical .smoke to determine whether the air flows out of the
building through leaks in nearby windows, doors, or other cracks and holes in exterior walls
• Use chemical smoke to determine whether air flows out of the building through below-grade cracks and holes (e g. fl oor
joints, pipe openings) «
EXHAUST SYSTEMS
Exhaust systems are used to remove air that contains contaminants, including odors. Some HVAC designs also rely on the
operation of exhaust fans to create negative pressure that draws outdoor air into the building through windows and gaps in the
building envelope.
19. Confirm that exhaust fans are operating
• Use chemical smoke to confirm that air is flowing into the exhaust grilles)
10 of 16
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20. Verify that local exhaust fans remove enough air to eliminate odors and chemical fumes
If the fan is intended to exhaust the entire room, stand outside the room with the door slightly open and use chemical smoke to
confirm that air is being drawn into the room from locations both high and low in the door opening (see How to Measure
Airflow).
If the fan is running, but air isn't flowing toward the exhaust intake (or too little air is moving to do the job), check for the
i following possibilities:
• The backdraft damper at the exhaust outlet does not open
• Obstructions in the ductwork
• Leaky or disconnected ductwork
• Brokenfanbelt
• Motor running backwards
• Design problems (e.g., undersized fan)
21. If the exhaust fan is located close to the contaminant source, rather than on the roof, and exhaust air is ducted
through the building under positive pressure
• Confirm that the exhaust ductwork is sealed and in good condition.
QUANTITY OF OUTDOOR AIR
22. Measure quantity of outdoor air per person
See How to Measure Airflow at the end of this Checklist for techniques on measuring outdoor air supply.
Measure the quantity of outdoor air supplied either to or from each ventilation unit. Use the Ventilation Log to calculate the
quantity of outside air per person being provided to occupants (22a. on the Ventilation Log)
Count or calculate the number of occupants served by the ventilation unit under consideration (22b. on the Ventilation Log)
Divide the quantity of outdoor air supplied by the number of occupants served for the ventilation unit under consideration (22a
divided by 22b on the Ventilation Log)
ADEQUACY OF OUTDOOR AIR SUPPLY
23. Compare the measured outdoor air per person to Table 1
In the first column of Table 1, find the listing for the type of area that is served by the unit you are evaluating
Check the second column to see if the occupancy for each 1,000 square feet that the ventilation unit serves is no greater than the
occupancy assumed for the recommendations
- Compare the recommended ventilation in the third column of Table 1 to the calculated outdoor air per person from Activity 22.
11 of 16
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If the calculated airflow is below the recommendations in Table 1, it may be that the school was designed to meet a lower
standard that was in effect at the time the school was built. If you have design specifications for the system or know code
requirements in effect at the time of construction, compare the measured outdoor air to this specification. Repair the system to
meet the design specification, if necessary.
If the school was designed to a lower standard and cannot meet the recommended levels in Table 1, discuss with the IAQ
Coordinator means for increasing ventilation:
• Retrofitting the ventilation system for increased capacity
• Opening windows (Caution: Consider potential ventilation problems that this may cause in other parts of the building)
• Make any repairs permanent and take any other measures that appear to help ensure adequate outdoor air in the future.
These improvements will probably require the services of a professional engineer.
Table 1: Selected ASHRAE Ventilation Recommendations
Type of Area CFM/person
Instructional Areas
Classrooms 50 15
Laboratories 30 20
Music rooms 50 15
Training shops 30 20
StaffAreas
Conference rooms 50-20
Offices 70 20
Smoking lounges 7 60
Bus garage: 1.5 CFM per square foot of floor area. Distribution among people must consider worker
location and concentration of running engines; stands where engines are run must incorporate systems
for positive engine exhaust withdrawal. Contaminant sensors may be used to control ventilation.
Assembly Rooms
Auditoriums 150 15
Libraries , 20' 20
Gymnasiums
Spectator areas 150 15 .•
Playingjloor 30 20
Food and Beverage Service
• Cafeteria 100 20
Kitchen 20 15
Additional airflow may be needed to provide make-up air for hood exhaust(s). The sum of the outdoor
air and transfer air of acceptable quantity from adjacent spaces shall be sufficient to provide an exhaust
rate of not less than 1.5 CFM/squarefoot.
Miscellaneous
Nurse's offices (patient areas) 10 25
Corridors: 0.1 CFM/squarefoot
Locker rooms: 0.5 CFM/square foot
Restroom:50 CFM/urinal or water closet
- SOURCE; ASHRAE Standard 62-1989, Ventilation for Acceptable Air Quality
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HOW TO MEASURE AIRFLOW
This section provides basic guidance and options for determining air movement and measuring outdoor air supply. It is divided
into three sections:
• Using chemical smoke to determine air flow direction
• Measuring airflow to determine outdoor air supply quantity
• Estimating outdoor air quantity using carbon dioxide measurements
1. Using Chemical Smoke to Determine Air Flow Direction
Chemical smoke can be helpful in evaluating HVAC systems, tracking air and pollutant movement, and identifying pressure
differentials. Chemical smoke moves from areas of higher pressure to areas of lower pressure if there is an opening between
them (e.g., door, utility penetration).
Because it is the same temperature as the surrounding air, chemical smoke is extremely sensitive to air currents. Investigators
can learn about airflow patterns by observing the direction and speed of smoke movement. Sirioke released near outdoor air
intakes will indicate whether air is being drawn into the intake. Puffs of smoke released at the shell of the building (by doors,
windows, or gaps) will indicate whether the HVAC systems are maintaining interior spaces under positive pressure relative to
the outdoors.
Chemical smoke is available with various dispensing mechanisms, including smoke "bottles," "guns," "pencils," or "rubes."
The dispensers allow smoke to be released in controlled quantities and directed at specific locations. It is often more informative
to use a number of small puffs of smoke as you move along an air pathway rather than releasing a large amount in a single puff.
Caution: Chemical smoke devices use titanium tetrachloride to produce smoke. While the chemicals forming the smoke nor-
mally are not hazardous in the small quantities produced during testing, avoid inhaling smoke from smoke devices. Concen-
trated fumes from smoke devices are very corrosive.
Determining Air Movement From Diffusers And Grilles
Puffs of smoke released near HVAC vents give a general idea of airflow. (Is it in or out? Vigorous? Sluggish? No flow'') This is
helpful in evaluating the supply and return system and determining whether ventilation air actually reaches the breathing zone.
(For a variable air volume system, be sure to take into account how the system is designed to modulate. It could be on during
the test, but off for much of the rest of the day.) "Short-circuiting" occurs when air moves directly from supply diffusers to
return grilles, instead of mixing with room air in the breathing zone. If a substantial amount of air short-circuits, occupants may
not receive adequate supplies of outdoor air and source emissions may not be diluted sufficiently.
2. Measuring Outdoor Air Supply Quantity
This section describes methods for determining the amount of outdoor air being supplied by a single ventilation unit using
either a Flow Hood or air velocity measurement device. These are general instructions for measuring airflow. Follow the
instructionsprovided by the manufacturer of your measuring equipment.
Step 1. Determine Airflow Quantity
Using a Flow Hood
Flow Hoods measure airflow in cubic feet per minute (CFM) at a diffuser or grille. Taking the measurement is simply a matter
of holding the hood up to the diffuser and reading the airflow value. Follow the instructions supplied with the Flow Hood
regarding use, care, and calibration
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Using Velocity Measurements
For information on measuring air velocity using a Pitot tube or anemometer and calculating outdoor air supply, see the instruc-
tions supplied with the equipment.
Airflow in large ductwork can be estimated by measuring air velocity using a Pitot tube with a differential pressure gauge or an
anemometer. (See the IAQ Coordinator for sources of these devices.)
• Measure the air velocity in the ductwork and calculate the outdoor airflow in cubic feet per minute (CFM) at the outdoor air
intake of the air handling unit or other convenient location
• Enter the calculated outdoor air supply in the Ventilation Log
For Systems Without Mechanically-Supplied Outdoor Air
If your-systeni does not have mechanically supplied outdoor air, you can estimate the amount of outdoor air infiltrating the area.
Estimate air infiltration by measuring the quantity of air exhausted by exhaust fans serving the area.
• Using a small floor plan, such as a fire escape map, mark the areas served by each exhaust fan
• Measure airflow at grilles or exhaust outlets using a flow hood. Determine the airflow in ductwork by using a Pitot tube
with a differential pressure gauge or an anemometer
• Add the airflows (in CFM) from all exhaust fans serving the area you are measuring and enter the measurement in the
Ventilation Log
A room can be positively or negatively pressurized when compared to the spaces surrounding it. These spaces
include another room, a corridor, or outdoors. To determine whether a room is positively or negatively pressur-
ized, or neutral, release puffs of smoke near the top and bottom of a slightly opened door or window, and
observe the direction of flow. Example: If the smoke flows inward at both the top and bottom of a slightly
opened door, the room is negatively pressurized when compared to the space on the other side of the door.
Negative pressurization may cause problems with natural draft combustion appliances, or cause outdoor
pollutants such as pollens or vehicle exhaust in loading docks to be drawn into the building through openings.
Negative Pressure Neutral Pressure Positive Pressure
Step 2. Determine Occupancy
Count the number of students and staff located in areas served by the air handling unit (called the occupied zone). If you are
estimating infiltration using exhaust fan airflows, count individuals in the area you have determined are affected by the fan(s)
in Step 1.
• Using a small floor plan, mark the occupied zone served by the unit. In areas served by unit ventilators, an occupied zone is
probably an individual classroom. In areas served by large air handling units, an occupied zone may include several rooms.
A large gymnasium or other room may be served by several air handling units.
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Estimate the number of occupants in the occupied zone, including students, teachers, other staff members, volunteers and
visitors.
Step 3. Calculate Outdoor Air Per Person
Outdoor Air (CFM) _ Outdoor Air
Number of Occupants (average CFM/
person)
• Use the equation below (the equation also appears on the Ventilation Log) to calculate average ventilation rates in CFM/
person
3. Estimating Outdoor Air Using Carbon Dioxide Measurements
Carbon dioxide (CO2) is a normal constituent of the atmosphere. Exhaled breath from building occupants and other sources
increase indoor CO2 levels above that of the outdoor air. CO2 should be measured with a direct-reading meter. Use the meter
according to manufacturer's instructions. Indoor CO, concentrations can, under some test conditions, be used to access outdoor
air ventilation. Comparison of peak CO2 readings between rooms and between air handler zones may help to identify and
diagnose various building ventilation deficiencies.
Step 1. Estimate quantity of outdoor air supply.
CO2 readings, with minimal delays between readings, can be taken at supply outlets or air handlers to estimate the percentage of
outdoor air in the supply airstream.
The percentage or quantity of outdoor air is calculated using CO2 measurements as shown below.
Outdoor air (%) = (CR-CS) - (CR-CO) x 100
Where: CS = ppm of CO2 in the supply air (if measured in a room), or in the mixed air (if measured at an air handler)
CR = ppm of CO2 in the return air
CO = PPM of CO2 in the outdoor air (Typical range is 300-450 ppm)
All these concentrations must be measured, not assumed.
To convert the outdoor air percentage to an amount of outdoor air in cubic feet per minute, use the following calculation.
Outdoor air (CFM) = Outdoor air (percent) •*• 100 x total airflow (CFM)
The number used for total airflow may be the air quantity supplied to a room or zone, the capacity of an air handler, or the total
airflow of the HVAC system. However, the actual amount of airflow in an air handler is often different from the quantity in
design documents. Therefore only measured airflow is accurate.
Step 2. Measure CO2 levels in the area served by a given unit or exhaust fan(s) or in an area
without any mechanical ventilation.
The number of occupants, time of day, position of windows and doors, and weather should be noted for each period of CO,
testing.
" • Measurements taken to evaluate the adequacy of ventilation should be made when concentrations are expected to peak It
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may be helpful to compare measurements taken at different times of day. Classroom CO2 levels will typically rise during
the morning, fall during the lunch period, then rise again, reaching a peak in mid-afternoon. Sample in the mid- to late-
afternoon
• Take several CO, measurements in the area under consideration. CO2 measurements for ventilation should be collected
away from any source that could directly influence the reading (e.g., hold the sampling device away from exhaled breath)
• Take several measurements outdoors
• For systems with mechanically supplied outdoor air, take one or more readings at the following locations:
- At the supply air vent
- In the mixed air (if measured at an air handler)
- In the return air
StepS. Note whether CO2 levels are high.
• Note locations with CO2 concentrations of 1,000 ppm or higher. Elevated CO2 indicates that there is not enough outdoor air
for the number of people in the space (based on ASHRAE Standard 62, see Appendix I of the IAQ Coordinator's Guide)
• Note that there may still be underventilation problems in rooms with peak CO2 concentrations below 1,000 PPM. CO2 is
produced by human respiration (breathing), and concentrations can change rapidly as people move in and out of a room.
Four to six hours of continuous occupancy are often required for CO2 to approach 'peak levels.
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