Danger. A word we are all familiar with, and something we face every single day, both at work and in our personal lives. Through our parents during our childhood, then over the rest of our lives through our own experiences, we learn about what can be dangerous to us. As you’d expect it often takes many years before we encounter the dangers of toxic gases, but once discovered, it’s imperative that we learn quickly.

What can injure us? What can kill us? How can we inadvertently hurt or kill someone else through our own actions? These are the types of questions we learn to ask ourselves, in order to keep ourselves and others safe from harm.

We can also “observe” areas or activities, and through education and training, we can see if any potential danger exists in what we are doing. A good example is driving a car. During this seemingly mundane task, we are constantly processing information to ensure nothing untoward happens. What are the current weather conditions? How fast are we going? What are the drivers around us doing? These are all things we can easily see, process and then decide upon the necessary action to take, if any. But what about the things we cannot see? Taking driving again; we cannot watch the engine as we drive the car, so how can we tell if everything is as it should be? From our position at the driver’s seat, we cannot see if there are any fluids leaking, anything is overheating, or parts are becoming loose or damaged. These are the sorts of hidden dangers that can catch us out and lead to catastrophic consequences. Just because as humans we cannot see it, smell it, feel it or hear it, does not mean it is not there. This leads us to the main focus of this article, the hidden dangers of gas.

There are many states of matter in our world, the most common three being solids (such as wood and paper), liquids (such as water and oil) and gases (such as nitrogen and hydrogen). Gases are all around us. They can be formed as a result of an industrial process, chemical reactions, or may simply be naturally occurring in the environment around us. We use them for many different purposes, such as heating or cooking in the home, or in certain industrial activities, such as hot works (Gas Cutting) and purging. These many different uses, however, come with many different problems.

Detecting the undetectable

Without assistance from technology some gases would be undetectable to humans, which understandably presents major health risks. According to an article from the Centers for Disease Control and Prevention published in 2018 (https://www. cdc.gov/co/faqs.htm), an estimated 400 people die in the US every year, with thousands more having to go to hospital due to poisoning from carbon monoxide gas. As this gas has no taste or smell and cannot be seen, exposure can lead to death through asphyxiation whilst people are sleeping.

Other gases are extremely flammable, leading to fires and/or explosions, a particularly severe risk when performing hot works (such as welding or grinding.) Some gases are heavier than air, which collect in low-lying areas such as trenches, pits and wells. This is a risk as often they can go undetected, through improperly testing for the gas, or simply not realizing it is there. Other dangers include the spread of gas to unprepared areas (such as gas released from a chemical plant drifting to nearby neighborhoods, putting the general public at risk) and adverse effects of gas being released into the natural environment, such as through acid rain, pollution of groundwater and so on. Even gases that are critical to our survival can be detrimental if they are present in the wrong quantity, just take oxygen as an example. Environments without oxygen, otherwise called oxygen deficient, we cannot survive; too much oxygen, an oxygen enrichment, can also be dangerous through increased fire risks as well as severe health effects such as oxygen toxicity.

So how do we find out if gas is present or not, and in what quantities? Well, predominantly by performing gas testing, and using gas monitoring systems. What exactly is appropriate depends upon the exact circumstances of the work. We may only need to perform an initial test to see if gas is present. We may need to perform several tests for several different types of gas. Gas may be present in the work area constantly, so performing one test simply would not be adequate.

Gas levels can fluctuate randomly between harmless and dangerous levels, hence needing to track measurements including:

  • LELs (Lower Explosive Limits)
  • UELs (Upper Explosive Limits)
  • TWA (Time Weighted Average)
  • PELs (Personal Exposure Limits)

  • You should be able to develop gas testing and monitoring procedures appropriate for your business through a suitable and sufficient risk assessment for the particular tasks or work area you are in. Again, due to the varied nature and effects of gases, you must ensure the persons developing these systems are competent. If you are not sure, seek expert advice and assistance.

    Testing versus monitoring

    Just to clarify the basics, let’s look quickly at what the two terms, ‘gas testing’ and ‘gas monitoring’, actually mean. Gas testing is a proactive measure involving using some type of equipment to “test” an environment for the potential presence of gases, usually before any work has started. Gas monitoring, on the other hand, is reactive, usually coming in the form of monitoring devices worn by personnel, or fixed systems on plant and equipment, used to constantly check the environment around the person or equipment to see what gas is present and at what level. If the level of gas becomes dangerous, these systems are usually alarmed in some way, to warn the workforce of the potential danger. Again, it is important to ensure that all persons involved in this process are competent, as any miscalculation or misunderstanding can lead to disaster.

    “stratification is where gases can be present at different levels of an environment due to their makeup”

    An example of this is a phenomenon called “Stratification”. This is where gases can be present at different levels of an environment due to their makeup. Let us use a confined space as an example. This space may contain hydrogen sulphide (H2S) gas. This gas is heavier than air, so will accumulate at the bottom of the confined space, whilst any other gases present will sit above it. So, if our authorized gas tester is not competent, he may only check the top half of the confined space, and declare it safe to enter. A competent gas tester would test the whole space, at all levels, detecting the presence of the H2S and therefore saving lives, by ensuring the space was purged and vented, re-testing the space afterwards to ensure all the H2S had been removed before any work started.

    Other issues that can occur involve the equipment itself. Often, testing and monitoring equipment is very sensitive, and therefore should be calibrated correctly for the task at hand. Using equipment that gives incorrect results will mean we make incorrect decisions about the safety of an area, particularly if those results show “safe” levels of gas. Earlier, I mentioned that our authorised gas tester should be competent. This is true, however, for any of our workers who are likely to work in areas where dangerous gases may be present. If workers are not trained on the dangers of these gases, how can they possibly know what the safe levels are, how to react to information provided by their personal monitors, and ultimately what to do in an emergency. In the past, this scenario has led to incidents in which several people lose their lives, all because they did not know any better.

    The incidents at Shah Field in the UAE in 2009 (H2S, three killed, one injured) and Valero Refinery, Delaware, USA on 6 November 2005 (Nitrogen, two killed) show just how much the magnitude of such tragedies can be greatly increased as workers attempt to rescue colleagues without, for example, the appropriate training and equipment.