Finding the bad air culprit: a first-hand look
Brown is the director of Workplace Health and Safety Programs for Cornell University's School of Industrial and Labor Relations. She was the guest speaker at the Spiral Duct Manufacturers Association (SPIDA) summer meeting held here in southeast Florida at the end of May.
Testing for mold is very much in vogue today, she said, since mold can be a source of problems in some buildings and has been garnering its share of media attention. "However, when they ask us to test for mold, I always ask them first, 'Have you had any roof leaks, or any evidence of standing water?' Chances are, if they say 'No' they don't have a mold problem. But they insist we test anyway, so we do."
As an investigator, Brown said she often relies on simple but inexpensive tools to perform her investigations, such as detector tubes and chemical smoke to show airflow. She demonstrated these devices. A detector tube, she said, will reveal the carbon dioxide (CO2) level in a room after a simple walk-around to sample the air in a room. The detector tubes are cheap, at around $4 apiece, but can only be used once and test for only one type of contaminant at a time.
Detected levels of 1,000 ppm or more in a room are not necessarily cause for alarm, but can be an indication of an underventilated room. She has encountered classrooms designed to meet minimum ASHRAE standards before those standards were increased: Today's thinking is that these rooms of five cfm per person are woefully underventilated and will make for drowsiness, inattention and a general perception of poor IAQ.
Acceptable levels of CO2She offered the following guideline on CO2 concentrations:
- 250-350 ppm: Normal outdoor ambient concentration.
- Less than 600 ppm: Minimal air quality complaints.
- 600-1,000 ppm: Less clearly interpreted.
- More than 1,000 ppm: Indicates inadequate ventilation; complaints such as headaches, fatigue, and eye and throat irritation will be more widespread.
Smoke tubes can be used to detect, among other things, if exhaust air in a room is indeed leaving through the exhaust vents, or if air is moving into a room from the inlets.
Often, your own nose can lend hints on what is causing the problem:
- "Sewer smell" (hydrogen sulfide gas). Cracked or blocked sanitary stack for toilet or drains.
- Dried out drain trap for sink, floor drain, toilet, etc. Sanitary stack located near air intake.
- "Fishy" smell (amine additive in boiler water) - Leak of steam or water from heating system.
- "Bottom of cat litter box" (decomposition of quaternary ammonium compounds) - Moisture/mold growth on fiberglass insulation.
Several times in her talk Brown emphasized that direct observation and a hands-on inspection is vital to a building investigation: You cannot assume a system is operating as it was intended to unless you see it for yourself.
She recalled one instance where adequate fan speeds were indicated on a computer readout. Upon inspecting the building's intake fans, however, she found the fans had been turned off many years ago to save energy. The fan speeds indicated on the computer readout were merely representations of what they had been in the past, rather than real-time current read-outs.
Often, solutions are almost absurdly simple. Upon investigating another school situation where occupants complained of a mysterious, foul odor, testing revealed hints of a cleaning product. "I asked if the custodians had possibly been using graffiti-removers in the hallways the night before," she said. Of course, they had.
Another time, it was a particular unbathed employee's own body odor that was causing the problem. Other employees knew it; they were just unwilling to confront the offender.
Scheduling occupancy to avoid such odor inducers as cleaning agents, paints, varnishes, etc. can often prevent IAQ complaints among building occupants. This includes outside use of chemicals too, such as pesticide applications for lawns and around building exteriors. Renovation work, if performed during occupancy, must be sealed off from the occupied portions of the building using plastic sheets, etc.
New products such as carpeting and room dividers can often off-gas formaldehyde, which can be an irritant when inhaled. Better to store the materials for a while before installation, and increase the ventilation in the rooms for at least several days after they are installed, to dissipate any contaminants until the materials can cure.
Brown offered the following recipe for addressing building IAQ complaints, one that she follows and says has proven useful to her:
Obtain information from building occupants
Phase I - Investigate the building
Check out the ventilation system
Find out if there is enough fresh air (verify with CO2)
Examine intakes and exhausts
Check out hvac performance and maintenance
Look for contaminant sources: inside, outside, biological, building fabric
Phase II (If needed to verify source or exposure) - Chemical analysis for air contaminants
Particulate measurement, with or without identification
Biological monitoring, with or without identification
Before doing monitoring, decide how the data will be interpreted. In the absence of applicable standards, you may decide to compare indoor air with outdoor air. If so, remember to sample the outside air.
It is helpful, even vital, to communicate with the building occupants throughout the investigation. She told of one building investigation that resulted in the need for hvac system improvements. However, while the project was out for bids, the occupants of the building grew more and more agitated, assuming that nothing was going to be done about the problem, increasing tensions and animosity with the building operators. Keep occupants informed on:
- The progress of the investigation, including the types of information which are being gathered and ways that they can help.
- The seriousness of the health problems being reported (this helps people to put their symptoms into perspective.)
- The estimated duration of the investigation.
- Attempts which are being made to improve indoor air quality.
- Work which remains to be done and the schedule for its completion.