Testing Indoor Air Quality: Humidity, Temperature and Carbon Dioxide

By | April 1, 2010

In today’s world the majority of us spend most of our time indoors. Whether at work, at home, out shopping at the mall, out to eat, or out to get wasted at a local tavern, it does not matter. The majority of us spend more time indoors than we do outdoors.

Therefore it should come as no surprise that the quality of the air we breathe matters and can have a pronounced effect on our wellness if the quality drops. We can get headaches, become ill, pass out, and even die (in extreme cases).

What Parameters Matter?

We won’t patronize you by listing off harmful gases and toxic fumes. If you don’t already know that sitting in an unventilated room with an open bucket of kerosene, toluene, paint thinner, etc. can seriously harm you… then we can’t save you.

Instead, we want to talk about temperature, humidity and carbon dioxide. The values of these three seemingly harmless indoor air quality parameters can make quite a big difference to people’s breathing comfort.

Temperature & Humidity:

There is no “ideal” humidity level and temperature suitable for all building occupants. Many factors, such as personal activity and clothing may affect personal comfort. Acceptable relative humidity levels should range from 20 percent – 60 percent year-round. Levels less than 20 percent in the winter and greater than 60 percent in the summer should be considered unacceptable. Elevated relative humidity can promote the growth of mold, bacteria, and dust mites, which can aggravate allergies and asthma. To achieve maximum occupant comfort, relative humidity should be maintained between 30 percent – 50 percent.

IDPH concurs with the ASHRAE guideline that indoor temperatures in the winter be maintained between 68 – 75 degrees, with a relative humidity level between 30 percent – 60 percent. Temperatures in the summer should be maintained between 73 – 79 degrees, with a relative humidity level between 30 percent – 60 percent. These ranges should be acceptable for sedentary or slightly active persons. ( source )

Carbon Dioxide:

Some of you probably think we meant to say ‘carbon MONoxide‘, but no, we said what we meant: Carbon Dioxide.

Carbon dioxide is a normal constituent of exhaled breath and is commonly measured as a screening tool to evaluate whether adequate volumes of fresh outdoor air are being introduced into indoor air. The outdoor level of carbon dioxide is usually 300 – 400 parts per million (ppm). The carbon dioxide level is usually greater inside a building than outside, even in buildings with few complaints about indoor air quality. If indoor carbon dioxide levels are more than 1,000 ppm, there is probably inadequate ventilation; and complaints such as headaches, fatigue, and eye and throat irritation may be prevalent.

Carbon dioxide itself is not responsible for the complaints; however, a high level of carbon dioxide may indicate that other contaminants in the building also may be present at elevated levels and could be responsible for occupant complaints.

Properly ventilated buildings should have carbon dioxide levels between 600 – 1,000 ppm, with a floor or building average of 800 ppm or less. If average carbon dioxide levels within a building are maintained at less than 800 ppm, with appropriate temperature and humidity levels, complaints about indoor air quality should be minimized. If carbon dioxide levels are greater than 1,000 ppm, complaints may occur. Therefore, 1,000 ppm should be used as a guideline for improving ventilation. If a building exceeds this guideline, it should NOT be interpreted as a hazardous or life-threatening situation. An elevated carbon dioxide level is only an indication of an inadequate amount of outside air being brought into a building. The level cited in this document should only be used as a guideline to determine the amount of fresh outside air entering a building.

In building areas where there are potential sources of carbon dioxide other than exhaled breath, the guidelines above cannot be used. Other sources can include exhaust gas from kilns, internal combustion engines, dry ice, etc. Under these conditions, the Occupational Safety and Health Administration (OSHA) standard for carbon dioxide should be used. The OSHA standard is an eight-hour time-weighted average (TWA) of 5,000 ppm with a short term 15-minute average limit of 30,000 ppm. ( source )

So as you can see, indoor air quality does matter and building managers, property owners, or perhaps even just a responsible department manager may want to check those parameters from time-to-time to make sure they have not drifted out of line.

OK, fine… Aside from avoiding potential problems w/ complaints from people in the building, uncomfortable or sickly employees typically get a lot less work done and make a lot more mistakes.

 Air Quality Meter: Digital CO2, RH, Temperature (CDM77535) with Case   CDM77535   Air Quality Meter: Digital CO2, RH, Temperature (CDM77535) with Case  $399.99
 Air Quality Monitor: Measures CO2 & Temperature (CDM1060)   CDM1060   Air Quality Monitor: Measures CO2 & Temperature (CDM1060)  $269.00
 Air Quality Monitor: Measures CO2, Temperature & Humidity (CDM77232)   CDM77232   Air Quality Monitor: Measures CO2, Temperature & Humidity (CDM77232)  $399.00
 Alarm: Radon Gas Detector & Monitor (HS71512) EPA Approved Pro Series 3   HS71512   Alarm: Radon Gas Detector & Monitor (HS71512) EPA Approved Pro Series 3  $129.95

Although we had not previously mentioned it, we felt the need to throw a radon gas detector into the above table. If you don’t already know why owning a radon gas detector makes sense, please check out the following links:


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