Finding Out What is Causing Poor Air Quality

An indoor air investigation involves a number of steps:

• inspecting the building; 
  
  
• collecting information from building occupants; 
  
  
• inspecting the heating, ventilation and air conditioning (HVAC) system; 
  
  
• reviewing drawings of the ventilation system; and 
  
  
• measuring the air for comfort factors and contaminants.
  
  

Inspecting the building

The best way to begin is to walk through the building. This will provide an opportunity to gather information in a number of ways.

1) Talk to your co-workers. Ask them what symptoms or complaints they have had. Find out when these problems occur and if they feel better after they leave the building.

2) Talk to the building maintenance staff. They often have useful information about equipment, the ventilation system, pest control, renovations and other activities. They can often help to figure out what changes might have taken place just before the complaints started to increase.

3) Look for problems as you go through the building. The following are signs of poor indoor air quality (IAQ).

• odors from dumpsters, garbage, food preparation, chemicals or stale air; 
  
  
• moisture damage or water stains on walls, windows, ceilings and floors; 
  
  
• visible fungal growth; 
  
  
• dust, soot and other dirt coming out of vents; 
  
  
• tobacco smoke; 
  
  
• dirty and clogged ventilation filters; 
  
  
• improperly stored chemicals; 
  
  
• unsanitary conditions or equipment; and/or 
  
  
• areas that feel too hot, cold or that have little air movement.
  
  

Collecting information from co-workers

Talking to your co-workers can help you figure out the problem. Sample questions to ask include:

• What kinds of symptoms or discomfort are you having? 
  
  
• Do you know other people with similar symptoms? 
  
  
• If so, who are they and where in the building do they work? 
  
  
• Do you have any health conditions that make you more likely to have problems with the air at work? 
  
  
• When did your symptoms start? 
  
  

There are times when a more detailed record of symptoms and complaints is needed. A sample “Interior Air Quality Occupant Survey” is included.

Inspecting the heating, ventilation, and air conditioning (HVAC) system

Troubles with the heating, ventilation, and air conditioning (HVAC) system are often the cause of IAQ problems. Common problems with the HVAC system include:

• not enough fresh air is brought in; 
  
  
• air is not properly heated, cooled, or dehumidified; 
  
  
• air is not distributed evenly through the building; and/or 
  
  
• air is not properly filtered and ducts are not clean.
  
  

The diagram in Figure 1 shows the basic parts of a building ventilation system.

Figure 1

Measuring the air for comfort factors and contaminants

Testing the air will confirm or rule out IAQ problems that show up during the walk through. The air samples that need to be taken include:

• Carbon dioxide: High levels of carbon dioxide are a sign of poor ventilation. Carbon dioxide levels of 1,000 parts per million, which is 3 to 4 times higher than outside air, indicate inadequate ventilation. 
  
  
• Relative humidity and temperature: Humidity should be between 30 and 60 percent. Depending on the season and the humidity, temperatures should be in the range shown below.
  
  

  Temperature and Relative Humidity Ranges During  Summer and Winter
  Relative Humidity	Winter Temperature	Summer Temperature
  30%	68.5°F - 76.0°F	74.0°F - 80.0°F
  40%	68.5°F - 75.5°F	73.5°F - 79.5°F
  50%	68.5°F - 74.5°F	73.0°F - 79.0°F
  60%	68.5°F - 74.0°F	72.5°F - 78.0°F

  
  
  
  
• Air movement: Simple measurement with a velometer can tell how much air is moving through a particular area. More sophisticated equipment is needed to balance the ventilation system. 
  
  
• Tests for specific chemicals in certain cases: Air samples may be taken if there is suspicion that certain chemicals might be causing symptoms or illness. Grab samples are taken using a handheld pump and tubes (colormetric) that detect the presence of a single chemical. 
  
  
• Tests for biological agents in certain cases: Testing for biological agents can be complex and expensive. Tests for biological agents are done if the walk through and the workers’ symptoms indicate that there may be biological contamination.