MIOSHA's Recommendation for Indoor Air Quality

Six Steps to a Healthy Indoor Environment

Step 1:   Set up a program to prevent indoor air quality (IAQ) problems.  Prevention means making sure mechanical systems are functioning properly and providing adequate ventilation to all areas of the building.  Also make sure that mechanical systems are properly cleaned and maintained. 

Step 2:   On a regular basis, inspect the building for water leaks and remove standing water from condensation pans of heating, ventilation, and air conditioning (HVAC) systems.  Excessive moisture in ducts, especially if they are lined with fiberglass, provides an environment conducive to mold growth that may spread throughout the mechanical system.  Installing high efficiency filters can help reduce the level of mold spores and allergens in a building. 

Step 3:   Where mold is discovered, treat the mold growth by removing the mold and treating the surface with a biocide.  Removing water damaged building materials such as ceiling tiles and carpets may also be required since they are difficult to clean. 

Step 4:   Train maintenance personnel.  Building maintenance personnel should receive training on how to maintain IAQ.  On a regularly scheduled basis, they should take ventilation measurements and check temperature, carbon dioxide, and humidity levels throughout the building to make sure they are within acceptable levels.  

Step 5:   Take complaints seriously.  Some building managers may dismiss complaints about IAQ when only one person complains.  However, everyone is different and a substance or toxin that affects one person may not affect others.  Cases have shown that ignoring IAQ complaints can lead to more severe and costly IAQ problems.  

Step 6:   Ventilate areas following renovation projects.  Paints, carpets, adhesives, pressed wood products, and furnishings can increase the levels of volatile organic compounds in the air for an extended period of time.  Prior to occupancy, thoroughly ventilate the renovation area with fresh outside air for three to four days.  When areas cannot be evacuated during renovation, conduct activities that produce contaminants (e.g., painting) during off hours when feasible and provide fresh air ventilation.

Recommendations for Addressing Indoor Air Quality (IAQ) Problems

1. Discuss with employees to determine what the problem is and respond accordingly.
2. If airborne contaminants are suspected, conduct a ventilation survey to determine the volume of outside air that is being added to the building circulated air.  The American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) recommends a minimum of 20 cubic feet per minute (cfm) of fresh outdoor air be added to the building circulated air, per building occupant, for standard office space.
3. Areas may be monitored for carbon dioxide (CO₂) which is produced by human respiration.  Levels greater than 1,000 parts per million (ppm) would indicate a need for additional fresh air according to ASHRAE guidelines.  The enforceable Michigan Occupational Safety and Health Administration (MIOSHA) permissible exposure limit (PEL) for CO₂ is 10,000 ppm.
4. Inspect the ventilation system to assure that moisture is not leaking into or being trapped in any part of the system.  Warm, moist conditions in ventilation systems can cause bacterial/fungal growth.  When warm air is drawn across cooling condensers, moisture is produced which is typically captured in a drip pan and piped to a floor drain.  Assure that drip pans are cleaned periodically and are pitched properly for good drain off.  Assure that drain pipes are not clogged, and that they are properly trapped to prevent sewer gases from being drawn into the system.  An outside firm may be contracted when necessary to clean the inside of ventilation ductwork.
5. Thoroughly dry or remove wet building materials when necessary, to prevent microbial growth.  Repair roof leaks, thoroughly disinfect flooded areas and in general prevent warm wet conditions that promote microbial growth.
6. An outside firm may be contacted to monitor for microbial contamination.  Currently, MIOSHA does not have the ability to monitor for microbial contaminants.
7. Investigate to assure that fresh air intakes are not located where contaminants can be drawn into the building.
8. Ensure that all ventilation system components;(e.g. fans, pulleys, belts, motors, and dampers), are periodically inspected and maintained to assure proper operation.
9. Ensure that all system filters are periodically inspected and maintained.
10. It is suggested that temperature and humidity be maintained in the following ranges:

¹Applies for person clothed in typical summer and winter clothing, at light, mainly sedentary activity.

²Humidities greater than 50% are considered unacceptable because of the potential for microbial growth.

SOURCE: ASHRAE (1981)