known as: Carbonic acid gas; Dry Ice; CO2; Diesel Exhaust Component
reference number (CAS): 124-38-9
What is carbon dioxide?
temperature, carbon dioxide (CO2) is a colorless, odorless, faintly
acidic-tasting, non-flammable gas. CO2 is the fourth most
abundant gas in the earth’s atmosphere. Depending on the
temperature and pressure, carbon dioxide can also exist as a liquid or a
solid. In its solid form, carbon dioxide is called dry ice because
it slowly changes from a cold solid directly into a gas.
Where is carbon dioxide found in the environment?
CO2 is a
byproduct of normal cell function. It is removed from the body via
the lungs in the exhaled air. CO2 is also produced when fossil
fuels are burned. Decaying vegetation can also produce CO2. Surface
soils can sometimes contain high concentrations of this gas, from decaying
vegetation or chemical changes in the bedrock. In its solid form,
CO2 is used in fire extinguishers, in laboratories, and in theater and stage productions as
dry ice to make fog.
How are people exposed to carbon dioxide?
build up in buildings that house a lot of people or animals, and is a
symptom of problems with fresh air circulation in the building or home.
Where CO2 levels in soils are high, the gas can seep into basements
through stone walls or cracks in floors and foundations. High levels
of CO2 can displace oxygen (O2) and nitrogen (N2), potentially causing
What conditions lead to high carbon dioxide levels indoors?
of carbon dioxide in a building is usually related to how much fresh air
is being brought into that building. In general, the higher the CO2
level in the building, the lower the amount of fresh air exchange.
Therefore, examining levels of CO2 in indoor air can reveal if the
heating, ventilation, and air conditioning (HVAC) systems are operating
within guidelines. CO2 levels are usually measured in percent (%) of
air or parts per million (ppm). High CO2 levels, generally over 1000
ppm, indicate a potential problem with air circulation and fresh air in a
room or building. In general, high CO2 levels indicate the need to
examine the HVAC system. High carbon dioxide levels can cause
poor air quality and can even extinguish pilot lights on gas-powered
The use of dry
ice in the work place can elevate indoor CO2 if the air is not
Will exposure to carbon dioxide result in harmful health effects?
CO2 can produce a variety of health effects. These may include
headaches, dizziness, restlessness, a tingling or pins or needles feeling,
difficulty breathing, sweating, tiredness, increased heart rate, elevated
blood pressure, coma, asphyxia, and convulsions.
The levels of CO2 in the air and potential health problems are:
- 350 ppm – background (normal) outdoor air level
1,000 ppm - typical level found in occupied spaces with good air
– 2,000 ppm - level associated with complaints of drowsiness and
– 5,000 ppm – level associated with headaches, sleepiness, and
stagnant, stale, stuffy air. Poor concentration, loss of
attention, increased heart rate and slight nausea may also be present.
ppm – this indicates unusual air conditions where high levels of
other gases could also be present. Toxicity or oxygen deprivation
could occur. This is the permissible exposure limit for daily workplace
- this level is immediately harmful due to oxygen deprivation.
How to avoid exposure
- Have an HVAC or
weatherization contractor measure CO2 levels within your home.
If the levels exceed 1,000 ppm, the furnace should be tuned to
increase levels of fresh air coming into the building. If levels
are above 2,000 ppm, this can be a serious condition that could
warrant HVAC modification.
- Never use a fire
extinguisher or dry ice in a manner by which it was not intended.
- Never enter a liquid
manure pit without protective equipment since CO2, along with ammonia,
methane and hydrogen sulfide generated from decomposing manure can
quickly cause loss of consciousness and death.
- Use care when entering
silos since CO2 can build up from the decomposing grain.
CDC websites on carbon dioxide
Building Air Quality: A
Guide for Building Owners and Facility Managers
(exit DHS; PDF, 2.8 MB)
Exposure to Carbon Dioxide
(exit DHS; PDF, 1.0 MB)
Biologic Effects of
(exit DHS; PDF, 3.3 MB)
This fact sheet summarizes information about this chemical and is not a complete
listing of all possible effects. It does not refer to work exposure or emergency
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