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 Carbon Monoxide (CO), is often called the “Silent Killer” because of its ability to take lives quickly and quietly when its victims never even knew they were at risk. It is indetectable to humans, being both tasteless and odorless, and in high enough concentrations it can kill within minutes. But CO is not so silent if you read about its victims in the news. It already claims hundreds of lives each year, and survivors of CO poisoning can be left with psychological and neurological symptoms. Sadly, this toxic gas takes lives that could be saved through education, awareness, and simple protection. Read this article to make yourself aware of the risks that CO poses, and how to stay CO safe!

What is CO And Who’s At Risk?
CO is a poisonous gas produced by the incomplete burning of carbon based fuels. When inhaled it deprives the blood stream of oxygen, suffocating its victim. No one is immune to the effects of CO, though children 14 and under are more likely to sustain poisoning than adults at lower levels. CO can cause immediate health problems, and even death, in high concentrations, and some suspect it can also cause long-term health problems in low concentrations if a person experiences regular exposure (such as at home, or in the workplace). Significant exposure to CO can also reduce life expectancy, as reported in a recent article of the Journal of the American Medicine Association.

Any gas or propane based engine will produce CO, meaning that boaters, truckers, and small aircraft pilots are at risk from CO fumes as soon as they start their vehicle. Homeowners suffer the most from CO poisoning, and are in danger from sources like gas-powered furnaces and water heaters, clogged fireplaces and chimneys, cars running in an attached garage, and burning of fuels indoors (such as a gas or charcoal grill). Travelers staying in hotels are in danger of CO poisoning as well, which can be leaked into a hotel room from nearby faulty heaters and boilers. To see examples of recent CO poisonings in all of these areas, and others, take a look at our news headlines page.

How Do I Know If I Am Being Exposed to CO?
The beginning symptoms of CO poisoning are sometimes compared to the symptoms of food poisoning. Depending on the level of CO, and length of exposure, you may experience any one or more of the following symptoms:

·         headache
·         dizziness
·         weakness and clumsiness
·         nausea and vomiting
·         quick irregular heartbeat
·         chest pain
·         hearing loss
·         blurry vision
·         disorientation or confusion seizures

Most people have experienced some of these symptoms at one time or another, which doesn’t necessarily mean that CO poisoning caused them. However, regular occurence of any of these symptoms might be an indication of CO poisoning. For example, do you suffer from any of these symptoms on a regular basis, or always in the same place? For example, do you regularly get headaches after entering your home, or when operating your vehicle. Do your symptoms go away when you leave the house or your vehicle? Have several members in your house been complaining of the same symptoms? If the answer to any of these questions is ‘yes’, then you might be suffering from the effects of CO exposure. But symptoms and problems don’t just appear when a person is exposed to high levels of CO. Even low-level CO concentrations can cause health problems if a person is exposed to them for long periods of time on a regular basis. This excerpt from an article published by the EPA explains why:

The health threat from lower levels of CO is most serious for those who suffer from heart disease, like angina, clogged arteries, or congestive heart failure. For a person with heart disease, a single exposure to CO at low levels may cause chest pain and reduce that person’s ability to exercise; repeated exposures may contribute to other cardiovascular effects.

Ultimately, the best way to determine if you are being exposed to CO in your environment, particulary in low-levels, is with a CO detector. Large, wall-socket CO detectors sold in hardware and drug stores may protect you from a high-level leak of CO in your home. Generally though, these detectors do not alarm at low-levels of CO, and also offer no way to measure the actual concentration. Also, to avoid false alarms, such detectors require several continuous minutes of exposure at high-levels before alarming. But by this time, you may already be suffering from the effects of CO poisoning – disoriented, sick, and wondering what is going on. Such home detectors also give you no way to test that they are still working. Don’t be fooled by the “Push to Test” buttons on these detectors. This button tests the audible alarm, but typically doesn’t check if the actual CO sensing element is still functioning. A better way to stay safe, both at home and when away, is with a portable CO monitor that has a digital readout. This allows you to monitor levels anywhere in your environment, no matter where you are. It also gives you the ability to routinely test the detector with a small source of CO (like a blown-out paper match, or CO bump kit). Learn more about the Pocket CO portable detector/dosimeter, a way to keep you and your family CO safe!

How Much CO is Too Much?

The level of CO concentration is measured using a system called Parts Per Million (PPM). For example, 100 PPM CO means that for every 999,900 molecules of air, there are 100 molecules of CO. CO effects people differently depending on the concentration. In addition to measuring the current level of CO concentration, another measurement used is the Time-Weighted Average (TWA). This measures your average exposure to CO over time, and is also measured in PPM. For example, if you were exposed to a large dose of CO in the begining of the day, but none afterwards, your TWA for the day would be low, since for most of the day you had no exposure. If, however, you are continually exposed to 20 PPM CO throughout the day, your TWA for the day will be 20 PPM.

The table below summarizes some health effects due to prolonged exposure to various concentrations of CO, as well as some government recommended limits, and Pocket CO alarm levels. It has been compiled from various sources, including the NFPA:

Level of CO

Health Effects, and Other Information


Normal, fresh air.


Maximum recommended indoor CO level (ASHRAE).

10-24 PPM

Possible health effects with long-term exposure.

25 PPM

Max TWA Exposure for 8 hour work-day (ACGIH).
Pocket CO TWA warning sounds each hour.

50 PPM

Maximum permissible exposure in workplace (OSHA).
First Pocket CO ALARM starts (optional, every 20 seconds).

100 PPM

Slight headache after 1-2 hours.

125 PPM

Second Pocket CO ALARM starts (every 10 seconds).

200 PPM

Dizziness, naseau, fagitue, headache after 2-3 hours of exposure.

400 PPM

Headache and nausea after 1-2 hours of exposure.
Life threatening in 3 hours.
Third Pocket CO ALARM starts (every 5 seconds).

800 PPM

Headache, nausea, and dizziness after 45 minutes; collapse and unconsciousness after 1 hour of exposure.
Death within 2-3 hours.

1000 PPM

Loss of consciousness after 1 hour of exposure.

1600 PPM

Headache, nausea, and dizziness after 20 minutes of exposure.
Death within 1-2 hours.

3200 PPM

Headache, nausea, and dizziness after 5-10 minutes; collapse and unconsciousness after 30 minutes of exposure.
Death within 1 hour.

6400 PPM

Death within 30 minutes.

12,800 PPM

Immediate physiological effects, unconsciousness.
Death within 1-3 minutes of exposure.

There are many CO exposure limits set by government organizations
. The American Society of Heating Refrigeration and Air Conditioning Engineers (ASHRAE) lists a maximum allowable short term limit of 9 PPM. And the EPA has set two national health protection standards for CO: a one-hour TWA of 35 PPM, and an eight-hour TWA of 9 PPM. These standards make it clear that any carbon monoxide reading over 9 PPM should be investigated and acted upon.

What Should I Do if CO is Detected?

With the Pocket CO you will be able to detect CO before being in danger of long term health effects. If you find out that a significant amount of CO is present, there are things you need to do for you and your loved one’s safety:

·         Turn off source of CO, if possible to do without endangering yourself or others. Then move to fresh air.

·         If indoors, move outside to fresh air immediately.

·         If you are outdoors, move far away from the source of CO (possibly a generator, outboard motor, etc.)

·         Call 120 if anyone is exhibiting symptoms of CO poisoning.


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