The Dangers of CO2

Carbon Dioxide (CO₂) is toxic, but the nature of the threat it poses is not always fully understood. People die needlessly every year in tragic and completely avoidable accidents.

Many national regulatory bodies set exposure limits above which employees must not be exposed. Personal gas detectors are designed to detect CO₂ to protect human life.

It is not possible to detect the presence of CO₂ other than by use of gas detection equipment.

Properties and effects of CO₂

CO₂ is heavier than air. It is a hazard throughout the manufacturing process. If CO₂ escapes, it will tend to sink to the floor, where it can form deadly, invisible pockets. It collects in cellars and at the bottom of containers and confined spaces, such as tanks and silos.

CO₂ IS EXTREMELY HAZARDOUS AND CAN KILL IN TWO WAYS:

• By displacing Oxygen (O₂), leading to rapid asphyxiation: Asphyxiation can be caused by any gas displacing O₂ leaving you with no O₂ to breathe in the atmosphere
• As a toxin: Not all gases are toxic. However, exposure to as little as 0.5% by volume CO₂ represents a toxic health hazard. 2% can cause headaches, whilst 5% can cause major breathing problems.

Concentrations greater than 10% by volume can lead to death. Because CO₂ is completely odourless and colourless, unless gas detection equipment is used, there may well be no indication of danger until it is too late.

Exposure Limits

Studies show that even in the presence of normal concentrations of oxygen, exposures to 7% CO₂ can cause death in only 5 minutes. While the data on the toxic effects of CO₂ are interpreted slightly differently in different jurisdictions, there is little meaningful difference. Many countries set statutory workplace exposure limits to protect against the effects of a toxic gas.

These are generally defined in two ways:
• Short Term Exposure Limit (STEL) – maximum allowable concentration over a shorter time period, usually 15 minutes
• Long Term Exposure Limit (LTEL) – calculated as an 8-hour time weighted average (TWA).

The TWA for CO₂ tends to be set around 0.5% with STEL between 1.5% and 3.0%. The TWA concept is based on a simple average of worker exposure during an 8 hour working day. It permits periods of exposure above the TWA limit, but only as long as the STEL is not exceeded and there is equivalent under-exposure to compensate.

Carbon Dioxide Displacement of Atmospheric Gases

There is still a misconception that by monitoring oxygen (O₂) levels, you are effectively protecting against CO₂. However, this is not the case, monitoring O₂ levels will only help protect you against asphyxiation. Reliance on monitoring levels of oxygen to protect against CO₂ could potentially lead to fatalities due to gas displacement.

Nitrogen (N₂) comprises the majority of normal air at almost 80% volume. This means that, if a CO₂ release occurs, most of the gas that it displaces will be N₂.

Therefore, in the event of a leak of CO₂, the percentage increase of CO₂ is not matched by a similar decrease in the O₂ concentration. CO₂ can reach exposure limit levels, but O₂ levels could still be comparatively unaffected and so considered safe.

Ensure compliance – Keep safe

In an environment where CO₂ is used in many different ways and likely to be regularly encountered, even if at low levels, how can people be protected from being poisoned by CO₂?

• Use gas detection equipment

  In order to ensure compliance with occupational exposure limits calculated as TWAs, it is necessary to monitor the levels of CO₂ each worker is exposed to individually through the use of personal gas detectors. Fixed gas detection systems can provide around the clock or continuous protection of the workplace.

Use of TWAs can also avoid false alarms, which cause unwarranted disruption. This prevents complacency which can lead to workers ignoring alarms or not turning on gas detectors. It should also improve operational efficiency.

• Detection in the breathing zone

  A personal gas detector should monitor the air that the worker is inhaling. To do this effectively, it must be worn in the breathing zone (within 30 cm of the mouth). Attached to the clothing collar, a hard hat or breast pocket is ideal, however, not on a belt or trouser pocket. Breathing on it directly must be avoided as this could set the gas detector into alarm.

• User-friendly detection

  A light and compact personal gas detector will encourage workers to wear it, comply and be protected. A bulky detector can be uncomfortable, heavy and restrict movement within a confined space which isn’t going to encourage the worker to wear it.

• Keep it simple

  When it comes to keeping safe, consider using a personal gas detector with simple button operation and you should be comfortable with how to use the gas detector. Some gas detectors provide warning action messages in the event of an alarm so you know exactly what to do. This means that if the gas detector does go into alarm, workers will be better placed to respond fast.

• Don’t miss the warning signs

  Some production areas are very noisy and poorly lit. A detector must combine powerful audible, vibration and visual signals to ensure the wearer is immediately alerted to danger, even in a noisy or dark environment.

• IR is best for CO₂

  Infrared (IR) sensors are better suited for industrial applications. IR sensors are not affected by high levels of gas, which some other gas sensors can be, making them more accurate and reliable. IR sensors are more robust, too. They offer a much longer life compared, to other commonly used sensor types, which also makes them more cost-effective when used in a portable gas detector.

• Ensure reliability

  Gas detectors are life-saving tools. For use in industrial environments, they must be tough to protect reliable electronics housed in impact-resistant casings.
  While the need to leave gas sensors exposed to the atmosphere means that no instrument can be fully sealed, a high degree of protection against dust and water ingress is essential.

• Maintain

  Whichever gas detector you choose, the importance of maintenance and calibration can’t be stressed enough. Regular bump testing (showing the gas detector gas) is the only way to check that a detector reacts correctly when in contact with gas. Personal gas detectors should also have a routine maintenance schedule which involves service, calibration and repair so it can be relied upon when needed.

Credit: Crowcon Instruments

Do you need to detect CO2? Contact a1-cbiss to talk to our technical specialists for help with your gas detection needs