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Improving Indoor Air Quality with CO2 Meters

Posted by Mark Lemon on

by Karthik Guduru


Carbon dioxide is a by-product of all life – we constantly exhale CO2 throughout the day. Although the amount we exhale individually is very small – about 0.02 cubic meters per hour – over a full working day, a typical office or classroom with 10 people will add over one extra cubic meter of carbon dioxide every hour. This raises the percentage of CO2 in the room very quickly, and is often miss-diagnosed as tiredness, inability to concentrate, lethargy, or even headaches. In fact, the pre-lunch slump that office workers or students feel may not be hunger, but may be the side effects of poor air quality.

A CO2 meter in the room can help to eliminate this by either warning the occupants of the high CO2 levels, or automatically adding fresh air into the room.

Types of CO2 meters

For the home, a hand held or portable CO2 meter is the most useful, as it can be used to test the air in different rooms at different times of the day by simply moving it. If the homeowner is concerned about a particular appliance like a wood stove or portable heater giving off too much CO2, they can set the meter next to it. If CO2 levels are too high, opening a window to allow in fresh air is the easiest solution.

In an office or a classroom, where the CO2 monitor should be tamper-proof, a wall mounted unit is best. A wall-mounted unit has the additional capability of being able to control a fan or a damper that will automatically add fresh air to the room as it is required.

The great thing about any kind of CO2 meter is that they are completely silent and unobtrusive. The NDIR technology (non-dispersive infrared) is accurate, self-calibrating and is designed to last for years with no maintenance.

Using a CO2 Meter

A CO2 meter is easy to use: simply read the CO2 level off the screen. For indoor air quality purposes, CO2 is measured in parts-per-million (ppm) which is the relative proportion of carbon dioxide molecules in a volume of air. For example

  • 100ppm = 0.01% CO2 
  • 390ppm = 0.04% CO2 (outdoor air)
  • 1,000ppm 0.1% CO2
  • 10,000ppm = 1% CO2
  • 100,000ppm = 10% CO2
  • 1,000,000ppm = 100% CO2

Note that outdoor air is contains approximately 390ppm, while OSHA and COSH guidelines worldwide recommend acceptable indoor CO2 levels between 800-1,000ppm. Therefore, any reading above 1,000ppm would indicate a lack of fresh air. In factories, the OSHA limit is 5,000ppm, which reflects the requirements of some manufacturing processes like welding, which uses compressed CO2. Indoor air quality CO2 meters normally measure up 5,000ppm, as levels above this in nature are extremely rare.

People who experience the health benefits of improved air quality never want to go back. The horrible feeling at the end of the day of a pending headache, tiredness and fatigue become a thing of the past - and all because the air in the room is fresh again.

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