Diagnosis

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Hypothosis

Diagnostic Process

Additional Resource: BAQ Guide

Additional Resource: Mold Assessment Guide

An IAQ investigation is like detective work - defining the problem, looking for clues, and finding a solution through an iterative process of narrowing the possible causes, and developing and testing hypotheses. The following graph is a representation of the process employeed at North Dakota State University when following the North Dakota State University IAQ Standard Operating Procedure (SOP).

Flow Chart Part 3

Clues may be found in basic information about the problem. Seeking the right information from occupants, examining building components with an educated eye, and making some simple diagnostic measurements can probably solve most problems.

By using data obtained from completed Employee IAQ Questionnaire(s) and data generated from the Questionnaire Evaluation Form the IAQ Coordinator can make conclusions regarding:

	What are the symptom patterns
	Where are the spatial patterns (where is the problem)
	What are the timing patterns (when do IAQ concerns occur)
	Occupant Patterns (who is the affected by IAQ concern)

What are the Symptoms?

Some symptoms or conditions suggest that certain causes are more likely than others are. Is the cause of the problem most likely to be a chemical source, a biological source, a lack of outdoor air, a thermal comfort problem, or not related to the building? In conjunction with the other information you obtain, use the table below to help narrow your first line of investigation. If the primary choice is not fruitful, go to the secondary choices.

Symptoms

Symptom/Condition	Potential Cause		Comment
Symptom/Condition	Primary	Secondary	Comment
Cough, congestion, chest tightness, shortness of breath, fever, chills	Biological	Chemical/particle	Check for microbial contamination in room/area, in the ductwork, in the cooling tower, or at the air handler Check for mold
Diagnosed infection or allergic disease	Biological	(none)	Obtain information about causes from diagnosis Check for microbial contamination in room/area, in the ductwork, in the cooling tower, or at the air handler Check for mold
Swelling, itching, skin rash	Biological (allergen) if small numbers involved Chemical/particle if large numbers involved	Chemical/particle if small numbers involved Biological if large numbers involved	Check for microbial contamination in room/area, in the ductwork, in the cooling tower, or at the air handler Check for mold Check for fiberglass contamination from insulation in ducts or around building envelope Check for renovation/remodeling sources Check for painting, adhesives, solvents, petroleum products in maintenance or housekeeping Check for aerosol products, cleansers, waxes in housekeeping Check major occupant sources such as printing, dry cleaning, hair salons etc.
Symptom/Condition	Potential Cause		Comment
Symptom/Condition	Primary	Secondary	Comment
Sinus headache	Biological (allergen), e.g. pollen, mold	Chemical particle	Could be allergen outside or inside. If outside, consider increasing filtration efficiency
Wheezing, asthma	Asthma triggers - dust mites - animal dander - pests - tobacco smoke - mold - ozone	(none)	For dust mites - Check dust mites - Keep relative humidity below 50% For animal dander - clean all surfaces - clean carpets and upholstered furniture For cockroach or rodent allergens: - institute or check integrated pest management procedures For tobacco smoke - ban smoking, or - check adequate operation of smoking lounge For mold - check for mold For ozone - Check information about outdoor ozone levels - Consider cleaning outdoor air brought into building - Check electrostatic precipitators or other electronic air cleaners which can produce ozone - Check for indoor ozone generating air cleaner See other responses associated with biological pollutants
Symptom/Condition	Potential Cause		Comment
Symptom/Condition	Primary	Secondary	Comment
Mild discomfort in eyes, nose, or throat Mild headaches General lethargy Generally not feeling well	Lack of outdoor air Temperature or humidity	Chemical/particle Biological	Check outdoor air Check thermostats Monitor temperature, and relative humidity Check for mold
Stuffy air	Lack of outdoor air Temperature too high and/or relative humidity too high	Insufficient air movement	Check outdoor air Check thermostats Monitor temperature and relative humidity Check volume of supply air
Too hot	Temperature and/or relative humidity too high Humidity too high Lack of outdoor air	Insufficient air movement	Check thermostats Monitor temperature and relative humidity Local heat source/high radiant temperature Check volume of supply air
Dry air	Temperature too high Humidity too low Particle pollutants	Lack of outdoor air	Check thermostats Monitor for temperature and relative humidity Check for dust or other particle sources Check housekeeping. Check over ventilation in heating season Too much infiltration/exfiltration Check outdoor air
Odors
Musty Stale air/body odor Dirty socks Sewer Petroleum Chemical (metallic taste) Gas fumes Pungent odor	Mold Lack of outdoor air/air mixing Dirty coils/filters, lack of outside air Sewer gas, drain traps, sanitary vents	Leaky tanks, spills Cleaning products, pesticides, preservatives Combustion spillage Particles burnt on a hot surface	Check for mold Check outdoor air Check coils/filters; Check for mold in air handler Check sewer gases, sewer line leak, soil air drawn from leach field, septic tank Check fuel tanks for leaks Check recent use of chemical products Check combustion spillage Check for particles burning on heat exchangers or hot baseboard heaters/radiators

Where Symptoms Occur

Are symptoms local to a given room, floor, air handling zone, side of the building, or are they widespread or scattered throughout the building? The possibilities are numerous. The examples below will help guide the user into the kind of investigative thought process (detective work) that can help find the cause(s) of the problem.

Where Symptoms Occur

Symptoms

Potential Source Examples

Potential HVAC Problem Examples

Potential Pathway Examples

Local

	Individual smoking
	Smoking lounge
	Kitchenette
	Printers/copiers
	Mold/moisture
	Storage area
	Local remodeling
	Furniture
	Outdoor sources near air intake of single zone air handler or local window/door
	Overcrowding in zone
	Significant heat sources (cooling loads) in zone
	Outdoor source entering outdoor air vent in single zone air handler
	Lack of housekeeping in the area

	Local exhaust
	Local diffuser
	Local thermostat
	Local air supply
	Contaminated local duct
	VAV box malfunction
	Problem in single zone HVAC system - contaminated filter - maintenance activity in - lack of outdoor air, etc.

	Local HVAC duct
	Source on lower floor/basement traveling up nearby stairwell/elevator
	Source elsewhere in the building coming through local penetration in wall/floor
	Room air
	Hallway

Interior zone

Source located in interior zone
- Copy room
- Mechanical room
- Storage closet
- etc.

Interior zone getting less supply air and outdoor air than exterior zones because thermal loads are less

(none)

Widespread

	Widespread modeling/renovations
	Building fabric/furnishings
	General housekeeping
	General building maintenance
	General overcrowding
	Significant heat sources (cooling loads) beyond central system capacity
	Outdoor source reaching all outdoor air intake vents, or vent of central air handler
	lack of outdoor air

	Problems (see above) with a central HVAC system
	Overall lack of HVAC maintenance
	Maintenance activity performed on all air handlers

Local source dispersed throughout building through central HVAC system

When Problems Occur

Looking for patterns in time, and then relating these patterns to various occupant or building activities, or to your knowledge of HVAC operations, can give clues as to the potential cause(s). The table below provides some examples of patterns and possible causes. It is designed to help the user understand how knowledge of the time pattern can help form a hypothesis of the cause. These are only examples.

Identifying Diagnostic Patterns

Pattern of Occurrence

Possible Causes

Mornings, (may be more severe on Monday morning), then dissipates as day/week progresses

	Failure to flush building at night and on weekends
	Late start-up of HVAC or late outdoor air damper openings during startup
	Morning traffic pollution entering outdoor air vent

Latter part of the week

Occupants or their activities may be the source, suggests possible inadequate outdoor air in HVAC to dilute pollutants.

Recurrent on a particular schedule

	Recurrent occupant/tenant or building maintenance or housekeeping activity which takes place just prior to the symptoms
	HVAC schedule/sequence related to symptom recurrence

Hot weather

	Emissions from recently installed furnishings.
	Inadequate HVAC capacity
	Economizer control malfunction

Mild temperatures

	Economizer controls malfunction
	VAV system at part load delivering little supply air and little outdoor air

Cool weather

Freeze stat control being tripped off

Does not go away when leave the building

May not be building related

Occupant Patterns

If it is just one individual, it may be that this individual is particularly sensitive to a contaminating agent in the building, or the problem may be local to their workspace. If all the individuals affected have a common preexisting condition such as a particular allergy, knowledge of their sensitivity may help find the cause(s) and may lead either to elimination of the causal agent or work arrangements that will minimize their exposure.

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