Imagine a threat to your safety that you cannot see, hear, or even smell. Now imagine that this hazard can kill you in seconds and may not be limited to the workplace. Now, image this invisible hazard can creep out of the workplace and kill you and your family while you sleep.

If this sounds like something out of a bad horror film, know that this actually happened, 37 years ago at a Union Carbide plant. The deadly chemical, methyl isocyanate leaked in a gas cloud that settled over Bhopal, India, exposing over 500,000 people – while most of them slept – creating the world’s worst industrial accident. Experts believe the death toll may have reached 16,000 men, women, and children who did nothing but go to sleep one night believing they were safe.

Gas exposure is one of the oldest and deadliest workplace hazards, and because it is often invisible and odourless it is a hazard that many people take lightly and it often costs people their lives. Also, because nontoxic gas can kill workers by displacing oxygen and making the air unbreathable many workers fail to take the necessary precautions. The best protection from injury from gas is knowledge. Knowledge of the properties of materials in a gaseous form, knowledge of the toxic gases that might be present in your workplace, and knowledge of what to do in the event of a potential exposure to the gas.

While many gases are undetectable to the human eye or nose, there are gas detection devices commercially available. One of the earliest forms of gas detection was the use of canaries that miners used to detect deadly gases; because canaries are smaller and more sensitive to gas the canaries would succumb to gas exposure before the toxicity level of the gas could harm the miners. Astonishingly, this practice continued until 1986, until modern technology replaced the ill-fated birds. Modern technology makes it relatively easy to detect gases and therefore avoid accidental exposure.

Gases can harm workers in a several ways. Some toxic gases form naturally during the process of extracting or processing raw materials in industries like oil and gas and mining; in other cases, deadly gases are either used in an industrial process or are a by-product of an industrial process. Some gases are even explosive, but experts estimate that exposure to toxic gases claims twice as many lives as those deaths caused by exploding gases. Clearly gas exposure is a potentially serious health and safety risk to workers everywhere, so early and accurate detection is of paramount importance.

Protecting workers from exposure

The best protection a worker can have against the harmful effects of gas exposure is to avoid the exposure altogether, and that takes situational awareness. Situational awareness is the practice of focusing on where you are, what hazards exist around you (for example, are you in a poorly ventilated area where gas is likely to collect? Or are you working around a vessel or pipe that might leak and expose you to gas?), the precautions you must take, and the PPE you must wear. Unfortunately, merely being situationally aware won’t be enough to protect you from an invisible and odourless substance that can kill you in seconds. To stay as safe as possible you must have a means to identify any and all deadly or toxic gases that might be present.

“some experts believe a worker is twice as likely to die from gas exposure attempting to rescue a worker who has already died from exposure to toxic gases”

There are two basic ways workers can detect gases: from fixed gas detection systems (stationary devices that detect gas levels in a given area that trigger alarms if gas is detected above a certain concentration) and portable gas detectors used or worn by personnel.

Waiting until toxic gas has been discovered is unwise, because the very properties of gas mean that it can expand quickly, collect in unexpected areas, or be diluted by a breeze below the threshold at which it can be detected. A better way to protect yourself and others from exposure to gas is to prevent the toxic gas from entering the workplace in the first place, but as is so often the case, this is more easily said than done. Gas – as a state of a material – acts very differently than solids and liquids.

According to experts in chemistry at Perdue University, gases have three characteristic properties:

  • They are easy to compress
  • They expand to fill their containers
  • They occupy far more space than the liquids or solids from which they form

What this means in terms of protecting workers from exposure is that even a small leak in a tank or pipe can release a high concentration of gas rapidly. Workers should be vigilant when working near areas where gases are stored or transported. Employers complete regular and thorough inspections of anything that contains or transports gas, and should remember to keep their gas detectors in good working condition and regularly check for signs of damage, corrosion, or other damage that could allow gas to escape. Also, these inspections should include any poorly ventilated areas in the vicinity of gas vessels because gasses expand to fill their containers. This means that a room, poorly ventilated area, or confined space can reach toxic concentrations of gas in a very short time. In addition to having alarms on these areas, companies should check these areas with portable detectors frequently and restrict access to these areas to essential personnel only. Workers should never enter a restricted area even though it appears safe to do so. This is especially true when you see a person lying on the ground. Some experts believe a worker is twice as likely to die from gas exposure attempting to rescue a worker who has already died from exposure to toxic gases.

Calibrating gas detectors

How do you know a gas detector is even working? If the gas is invisible, odourless, and lethal you can’t tell if a device is working by visually inspecting it. Often the fact that an alarm never sounds (or worse yet, sounds when no gas is actually present) can lead to workers to be complacent. In fact, it is not uncommon for workers to disable alarms that sound too frequently because of ‘alarm fatigue’ – a condition in which workers grow irritated by the sound of alarms that are not really indicating the presence of gas; this is an extremely foolish, irresponsible, and dangerous action that recklessly endangers lives.

To be sure that workers are kept safe, both portable and fixed gas detectors need to be calibrated often. While one should always follow the manufacturer’s recommendations for calibration it is always a good policy to include calibration of all gas monitors on a TPM schedule. Also, in the event that the circumstances of your use of gas or the physical configuration of your site should change (or if someone has tampered with or modified a gas detection device in any way) it is essential to contact the manufacturer immediately to ensure that the device is still viable and appropriate in this new situation.

Never assume that a gas detector is in good working order and be mindful of the risks. Stay out of areas that you don’t need to enter and always wear the appropriate PPE. Remember gas often doesn’t appear dangerous until someone is seriously injured so be prepared to act before you need to.

Emergency planning

The time to consider how to deal with an emergency that has the potential to expose workers or the surrounding community is well before anything happens. In the case of a gas leak seconds count so a quick, decisive, and orderly response is essential, and this begins with a good Emergency Action Plan (EAP).

An effective EAP (note: some of these tips for an effective emergency action plan first appeared in the August 11, 2016 edition of Health and Safety Middle East) should include:

  1. Clear and unambiguous triggers for executing the plan. As mentioned earlier in this article, in a gas leak seconds count, so no time can be lost deciding whether or not to respond to the incident. It should be made very clear the criteria for executing the EAP.
  2. Definitive identification of the ‘personin- charge’ of both the EAP, and the chain-of-command. When everyone is responsible for something, then no one is really responsible. A good EAP will identify the ultimate owner of the plan and a chain-of-command so that everyone knows who will be doing what, and who assumes an absent team member’s duties.
  3. Evacuation procedures and identification of all exit routes. In general, a single evacuation route is neither advisable nor effective, but in many cases geography may limit your ability to have an alternate evacuation route. The evacuation route should identify rally points where workers gather after the site has been evacuated so all workers can be accounted for, and evacuation routes should be posted in multiple areas of the site.
  4. First-aid and rescue duty assignments. While the plan must identify qualified first-aid and rescue duty assignments, it should also make it very clear that no one should attempt a rescue of someone who may have been exposed to gas without first donning the proper PPE.
  5. All employees should be allowed to sound the alarm if they even suspect the release of a toxic gas and the EAP should define the process and procedure for stopping work and sounding the alarm. The suspected area should be restricted until it can be proven free from hazards.
  6. Procedures for employees who remain behind. In some cases, some workers will be required to remain behind to shut off equipment, ensure toxic or explosive chemicals are secured, or wait with an injured worker until first responders arrive. In these cases, strict protocols designed to subject these workers to the lowest possible risk are essential.
  7. Procedures for accounting for all employees after evacuation, or upon a shelter-in-place emergency. Once at the rally point, the person in charge of implementing the EAP must have a means of quickly ascertaining who is present and who is absent. Often first responders needlessly risk their lives, and even lose them, looking for someone who had already vacated the premises.
  8. Procedures for critical operation shutdown. In many cases, the site simply cannot be hastily abandoned and critical operations must be shut down before the site can be evacuated. The emergency plan must clearly identify the “who?” “what?” “why?” “where?” and “how long?” of the procedure for shutting down critical operations.

Even in industries where it is common to have temporary work sites, if gas is a known danger, all sites should have frequent practice drills in how to respond to an emergency. By having frequent drills workers become able to execute emergency procedures without even thinking. Drills also tend to allow workers to remain calm during an actual emergency and better able to survive and even avoid exposure to toxic gasses.


The best EAPs are completely useless without comprehensive training in the dangers presented by the deadly gases and how to quickly protect you from them. Something as simple as knowing how to tell which way the wind is blowing and how to move out of the path of a gas cloud can mean the difference between life and death. For example, moving upwind through the gas cloud exposes you to the gas, while moving downwind will cause the gas cloud to follow you. In many cases the safest thing to do is to move crosswind (to the left or right from the direction the wind is blowing) so that you can avoid the gas cloud altogether.

Training should be provided to anyone who has the potential to be exposed to gas including:

  • Workers
  • Visitors
  • Contractors, and in some cases
  • The community

The training should include the names of all the potentially harmful gases used or produced on site, the dangers presented by the gases, emergency first aid for treating someone who has been exposed to the gas (if applicable), alarms and what one should do if an alarm sounds, areas where gas is most likely to be present, and a complete review of the Emergency Action Plan.