Many toxic indoor air environments need our attention. Indoor air quality can be affected by microbial contaminants (mold, bacteria), gases (including carbon monoxide, and volatile organic compounds), and particulates (dust, dirt, pollen). With all of these pollutants, it’s no wonder indoor air is becoming more of a health hazard than outdoor air.
These toxic environments affect our health with headaches, coughing, sneezing and trigger allergies and asthma. Since we spend 80 to 90 percent of our time indoors, poor indoor air quality in homes, offices, medical clinics, beauty salons, schools, and hotels is a concern. Simply being aware, and using our noses to monitor when indoor air quality is poor, is a good start.
Maintaining indoor air quality is a delicate process that can be affected by many variables. Indoor air pollution is caused by a long list of products and activities, including combustion sources, building materials made of pressed wood products, items containing pollutants like asbestos, cleaning products, improperly maintained central heating and cooling systems, and humidification devices.
Additionally, when there isn’t an effective air change rate, (the rate indoor air is replaced or filtered in a defined space) indoor pollutant levels can increase. The volume of “changed” air required for proper indoor air quality is determined by the size and use of the space. The table below gives recommended change rates(air changes per hour) in some common types of rooms and buildings:
| Building / Room | Recommended Air Change Rates per hour |
| All spaces in general | 4 times minimum |
| Beauty Shops | 6 – 10 times |
| Medical Clinics | 8 – 12 times |
| Offices, private | 4 times |
| School Classrooms | 4 – 12 times |
Air Change Rates can be calculated with n = 60 q / V
- n= desired air change rate per hour
- q = changed airflow through the room (Cubic Feet per Minute,cfm)
- V = volume of the room (Cubic Feet)
If you have an air purifier delivering 265 cfm of air to your office measuring 20 ft. x 15 ft. with 8 ft. ceilings (2,400 cubic feet), the air change rate would be calculated as follows:
- 60 x 265 (cfm) / 2,400(volume of room) = 6.63 air changes per hour
The air change rate is managed through natural and/or mechanical ventilation. Natural ventilation occurs when air moves through opened doors and windows by wind or temperature differences. Mechanical ventilation occurs when air handling systems or air purifiers change the air. A proper air exchange rate is vital for maintaining healthy indoor air.
The air change rate is very important because indoor pollutants can add up and create unhealthy indoor air. With buildings being built airtight for energy efficiency, often the air change rate is insufficient. There are measures one can take to restore poor air quality:
- Control the source of the pollution: Eliminate individual sources of indoor air pollution. This is low-cost and effective.
- Improve ventilation: Increase your air change rate through simple actions such as opening windows more often.
- Properly utilize and maintain air treatment equipment: A well-designed and maintained HVAC system and individual air purifiers can maintain an effective air change rate to remove indoor pollutants.
Even with the toxic indoor air we inhale every day, having an effective air change rate will greatly improve indoor air quality and the health of the occupants. Remember, a minimum of four air changes per hour for all indoor spaces is required for a healthy environment. The importance of a proper air change rate cannot be understated. Better indoor air makes us feel better, stay healthier, and breathe easier.
References:
- 1. http://www.engineeringtoolbox.com/air-change-rate-room-d_867.html
- 2. http://en.wikipedia.org/wiki/Indoor_air_quality
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