Detecting Danger

Gas testing and monitoring

by James Pretty

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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 realising it is there. Other dangers include the spread of gas to unprepared areas (such as gas released from a chemical plant drifting to nearby neighbourhoods, 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 authorised 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.

The equipment itself

So, we talked earlier about gas testing being performed incorrectly due to equipment being used by untrained persons, but what about the equipment itself?

Well, as with anything in health and safety, this equipment can come in many different forms, and what is right for your business depends upon your circumstances. You may only be worried about a relatively small quantity of one single particular gas, so a gas tube sampling system may be adequate. This system is comprised of a hand-held pump, with a glass tube inserted into the end of it. When using these systems, a person holds the pump in one hand, and the pump handle in the other. They then take a reading from a space by simply pulling the handle all the way back, drawing sampled air from the space/atmosphere into the tube.

These glass tubes contain a reactive element or reagent that will change colour if a gas is present, and will also give an indication of how much gas there is through a measurement scale marked on the tube. The advantages of these systems are that they are relatively easy to handle and use, requiring a minimum amount of training, and are relatively low cost compared to other solutions. As they have no electrical parts, they also do not present a fire risk, as they produce neither heat nor sparks. They do, however, have some limitations.

“gas detection systems require maintenance and regular calibration to ensure a true reading”

The tubes are each specific to one type of gas only, so several different tube types would be required to test for different gases. The tubes are also very delicate and break very easily. As they require a person to hold and operate them, this presents problems if trying to test large spaces, as the person testing for gas can only test places they can physically reach. Sampling tubes will also only tell us the amount of gas present at that very moment in time, and cannot monitor the air; once a sample is taken, the tube has to be replaced with a new one. These systems were first developed back in the 1900s, and whilst technology has greatly improved, they are still manufactured and in use today.

If you want to test for multiple gases, or have more complex hazards to deal with, a multi-gas detector is probably your best option. There are thousands of manufacturers all around the world who make these pieces of equipment, suited to specific industries or for more general applications. They work by testing and monitoring the air around them, but unlike sampling tubes, they can ‘analyse’ a sample of air for multiple gas types. Unlike a sampling tube, these testing and detection systems can be fixed to certain areas of plant or equipment if required, and are able to be used to test varying levels of an atmosphere, without putting the user at risk. As an example, a gas tester may be using a device with a long tube attached to it. They can lower the tube into the atmosphere to be tested, without physically entering the potentially deadly atmosphere themselves. Also, if gases are found to be at dangerous levels, these machines will instantly alert people to the danger. This alert will come through both an audible alarm and lights on a visual display. Usually, this alert will occur at a level where workers are able to “down tools” and escape the environment, before it becomes too dangerous. Another advantage these systems have is the fact that, as well as being used for initially testing an atmosphere, they can be used for real-time monitoring of the air, meaning we can have knowledge on whether and to what extent gas levels are fluctuating. Like anything else these systems can present issues. Without correct training, they can be very complicated to use; however, lots of manufacturers are pushing towards one-button operation. They also often require maintenance and calibration to ensure they are giving us a “true” reading of the gases present around them. Particularly for environments that present a fire or explosion hazard, these pieces of equipment must be “intrinsically safe”. In other words, they must be designed in such a way that their use will not cause flammable gases to ignite. You can usually tell this by the markings on them, such as (EX) or ATEX, meaning explosion proof. This does not mean they will survive an explosion, rather that they are designed in such a way as to not cause one. These systems can be portable, which can present issues with batteries running out, and equipment being damaged through rough use or being dropped.

Monitoring can also be done through the use of personal monitors. These machines are solely for the purpose of monitoring the environment directly around a specific worker, usually being positioned around the breathing zone of the individual. These are particularly useful when gas testing is intermittent, and as a contingency in case there are issues with other gas testing and monitoring systems. They are also useful for investigating where potential leaks may occur. A group of workers may be working together in a specific area, but only one or two of them are exposed to the hazardous gas, indicated to us by the fact their monitors sound an alert when none of the others do.

Personal monitors are also useful for monitoring the health of workers. As with other systems, these will activate when gases reach certain levels, but all of us are different in terms of the volume and duration of substance exposure we can tolerate. The workers can look at the level indicated on the monitor, and inform us of the level of gas to which they were exposed, helping us to further develop safe systems of work (SSOW) including permit to work systems, training regimens and written procedures, and occupational exposure limits (OELs) to be appropriate to our workforce, of course, bearing in mind any legal requirements.

“personal monitors are relatively easy to use also, once workers have been trained how to use them and what to look out for”

Many companies in the oil and gas industry set their personal monitors to alarm at 10 parts per million (PPM). We may, however, decide to have our systems set at 5ppm, providing an extra safety factor for the workforce and allowing them to evacuate before any ill-health effects occur. Personal monitors are also relatively easy to use, once workers have been trained how to use them and what to look out for in terms of readings on the visual display and alarms (usually lights, sounds and vibration). Again, however, they do have issues we need to be aware of.

Much like gas detectors, monitors have to be regularly calibrated and maintained to ensure they are giving us accurate readings. There can also be issues with batteries losing power during the working shift, or being lost altogether. Another big issue is the potential for accidental or deliberate misuse by the workforce. Some workers may forget to wear them, or wear them in a totally inappropriate place. A monitor worn on a hard hat or hip pocket can easily be knocked off the body, and it would be difficult to know if it had activated when placed onto that body position. Like any portable equipment, they can also be damaged through being dropped or miss handled. Using the wrong type of personal monitor could also mean hazardous gases go undetected, so if multiple gases are present, a multi-gas personal monitor will be required. Again, remember that gas monitors are a “mitigation” device, they will not prevent the release or presence of gas, only inform us it is suddenly there. Gas testing can at least be used to give us an indication of any gas being present before work starts, hopefully preventing many gas related incidents and accidents from occurring in the first place. I would recommend you visit the official United States Chemical Safety Board (USCSB) website (www.csb.gov) for more examples of incidents, gases and gas testing.

Closing thoughts

Gas testing and monitoring does not have to be a complex operation, but it is crucial to undertake this correctly if we are to stay safe when working with, and in environments containing, gases.

As always, risk assess your workplace and tasks, looking specifically for gas-related hazards. This will then arm you with key information in developing your approach to dealing with the hazards you have identified. Also, consider other control measures. Can you do the work without using the gas? Can you replace the gas with another that is less hazardous? Is there a time when the gas is at safer levels than other times? Provide information, instruction and training to everyone who may be potentially affected by your work with gas, not just your workforce. Ultimately, always have practiced emergency arrangements ready to go so you can mitigate the circumstances, should the worst happen.
As always, seek help from experts on the gases you use and the type of work you are doing, so that you can acquire the necessary gas testing and monitoring equipment you will need to detect and deal with the dangers of gases.

Author Details

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James Pretty

HSE professional, holding Technician status with the Institute of Occupational Safety & Health (TechIOSH). James is an approved NEBOSH and IOSH Trainer, and specialises in Materials Handling Equipment Training, for which he is a qualified instructor through ITSSAR (International Trading Standards Scheme and Register), and RTITB (Road Transport Industry Training Board).