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.
| Symptoms |
Potential Source Examples |
Potential HVAC Problem Examples |
Potential Pathway Examples |
Local
|
- Outdoor sources near air intake of single zone air handler or local window/door
- 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
|
- Source on lower floor/basement traveling up nearby stairwell/elevator
- Source elsewhere in the building coming through local penetration in wall/floor
|
| 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
|
Identifying Diagnostic Patterns
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.
| 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.
- 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
|
Who Experiences the Problem?
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.
Diagnosing and Solving IAQ Problems: Where and When Do the Problems Occur?
Created on November 21st, 2011. Last Modified on February 10th, 2012The Healthy Facilities Institute provides the information on HealthyFaciltiesInstitute.com as a free service to the public.
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