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There are many hazards and incidents that we can face in our daily lives. Whilst many of these would be thought of as “workplace” hazards and incidents, they can actually cross over into our everyday lives.
Fires are certainly the one that scares me the most, as these can occur in any home or business, anywhere, at any time. Crucially, these fires and explosions often have such catastrophic consequences that businesses simply never recover and homes are destroyed, and they only have to happen once for this nightmare scenario to occur. Our discussion today is on the topic of working in areas where these events may occur, and the disastrous consequences that result.
Most importantly, we will discuss some of the things we can do to avoid being in the same situations, and some of the options we could employ to mitigate the impacts of these incidents, should they occur.
“fires and explosions can have such catastrophic consequences that businesses never recover”
There are many, many, many, many, many, (…you get the idea) examples of major incidents occurring with “explosive atmospheres”. I would urge all of you reading today to go and look at as many examples as you can, to learn from the incidents. Some in particular that I recommend researching include:
- Buncefield Oil Refinery Explosion – Hemel Hemsptead, UK, 2005 (the explosions in this incident caused the largest fire in Europe since the second world war) https://www.hse.gov.uk/comah/ buncefield/index.htm (Here is plenty of information on the incident from the UK’s Health & Safety Executive)
- Texas City – Refinery explosion in Texas City Refinery, Texas, USA that occurred in 2005, killing 15 people and shutting down part of the plant for two years https://www.youtube.com/ watch?v=XuJtdQOU_Z4 (Here is a video on the investigation, conducted by the USCSB, United Stated Chemical Safety Board) https://www.youtube.com/ watch?v=goSEyGNfiPM (Here is an updated computer animation of the same incident)
- Imperial Sugar – Port Wentworth, Georgia, USA. Dust explosions and fires that killed 14 workers in 2008, and required the facility to be totally rebuilt https://www.youtube.com/ watch?v=Jg7mLSG-Yws (Here is the video on the USCSB investigation)
- Pike River Mine – 19 November 2010, a series of Methane Explosions occurred in an underground coal mine, 46 km from Greymouth, New Zealand, trapping and killing 29 mine workers. To this day sadly, the bodies of the victims have never been recovered (incredibly two workers survived, walking 2km to safety). https://en.wikipedia.org/wiki/Pike_ River_Mine_disaster (here is a Wikipedia article on the disaster)
I have included the Imperial Sugar and Pike River incidents as many people always assume that explosive atmospheres are only found in the petrochemical industries. This simply is not true. It is important to note that an explosive atmosphere can occur anywhere, providing you have the right mixture of fuel (any combustible substance) and air, and a source of heat/ ignition. Indeed, OSHA (the Occupational Safety and Health Administration of America) were actually trying to strengthen their regulations surrounding explosive atmospheres and combustible dusts, just prior to the occurrence of the Imperial Sugar incident. Also, a quick online search will show you just how often people become victims from explosive atmospheres in their own homes, after gas explosions from faulty home heating systems, and kitchens that use gas as fuel. So how can we actually classify an explosive atmosphere?
Classifying explosive atmospheres
As I mentioned earlier, it is all about having the right mixture of fuel and air together that can be ignited. It is a bit of a mouthful, but if you want a more detailed definition, according to the UK HSE’s DSEAR (Dangerous Substances and Explosive Atmospheres Regulations 2002), an explosive atmosphere can be defined as any atmosphere that has:
“…a mixture of dangerous substances with air, under atmospheric conditions, in the form of gases, vapours, mist or dust in which, after ignition has occurred, combustion spreads to the entire unburned mixture.” Often experts in this field will refer to the mixture being between the LEL (which means Lower Explosive Limit) and UEL (which means Upper Explosive Limit). If the mixture is below the LEL, this means there is not enough fuel for an explosion (or the mixture is to lean). If it is above the UEL, this means there is simply too much fuel and not enough air (the mixture is too rich). One of the concerns with this, is that the mixture of the substances can change, so one of the weapons in our arsenal that is vital for safe working in explosive atmospheres, is gas testing and detection.
Testing issues
Competent testers
First of all, gas testing itself must always be carried out by competent people, who will have undergone some form of training. This is critical as any miscalculations can spell disaster. Workers may misinterpret data and information being provided by the equipment, or they may use it in the wrong way. Let me give you
an example. Let us imagine we wish to perform some welding and repair work on top of a storage tank. Our gas tester climbs to the top of the tank and measures the area around the top of the tank, looking for flammable gas. He finds nothing and declares it safe to start the job. We then send our team of two welders onto the tank to carry out the work required. Next thing you know, we have an explosion that kills one of the welders, and seriously injures the other one. I would like to say this is a totally hypothetical scenario, but unfortunately this exact incident happened at a DuPont Chemical Facility in Buffalo, USA in 2010.
(https://www.youtube.com/ watch?v=PqskpvPejeU) (here is the video of the USCSB investigation.)
Stratification
Another issue that can cause problems with gas testing, is something called Stratification. This is where you get separate layers of different gasses within different parts of a space, due to their different properties. Hydrogen sulphide gas (H2S) for example, is heavier than air, so will always be in lower lying areas. If we only measure the top portion of an area we want to work in, we would never know it was there.
“Pump and Tube” system
Another issue to consider is the equipment itself. Gas testers and detectors come in myriad shapes, sizes and types. One that you may have come across is the gas “Pump and Tube” system. Whilst this is fairly “old-school” compared to some equipment, it is still widely used in industry today. These work by placing a glass tube, containing some form of reactant or re-agent, into a pump. A worker then points the open end of the tube towards the area they want to test. They then pull on the handle on the pump, and this draws air into the tube. Once this is done, they can then look at the tube.
The reagent will have changed colour or had some other reaction, which allows the worker to take a reading of what they have “sampled” by looking at the markings on the tube. While the main advantage with these systems is their relative ease of use, they can only sample a very small area. Effectively, they also only take a “snap-shot” of what is going on, rather than doing realtime, constant measuring and monitoring of the area. The fact that the tubes are constructed of glass means they are fragile and prone to breaking. Also, they can only be used once, so you need to have plenty of tubes to hand. The reagent will also only detect one specific type of substance, so you would need multiple tubes with different reagents to take measurements of different substances.
Electronic sensors
In comparison, the electronic gas detectors and multi-meters have very sensitive electronic sensors in them. (However, for measuring dust, the equipment would have weighted filters to collect dust, or would use a “lightbeam” system to measure the concentration of dust particles in the air). Not only can these systems give very accurate readings, most of them can also do constant monitoring, rather than the snapshot of the pump-and-tube system we discussed earlier. Another advantage of these systems is that they can either be mobile (being carried by a worker), or they can be fixed in place in key locations around plants and facilities where we believe there is the highest risk of the presence of flammable substances. These systems can also come in the form of personal monitors, so they can help monitor the area
around the workers, rather than just the work area itself. However, as always, nothing is infallible. I have already mentioned before about the issues with the actual use of the equipment by the workers. Other issues can include the equipment itself giving incorrect readings due to poor calibration, or damaged sensors, batteries can run out on mobile equipment, and the equipment can become damaged through being dropped (or being struck by something in the case of fixed detectors. Fixed detectors, in particular, would also have to be weather proofed to cope with the effects of wind, rain and so on).
“issues with gas detection equipment can include the equipment itself giving incorrect readings due to poor calibration, or damaged sensors”
Risk assessment
So, before we even consider what equipment we need, it is vital that we first conduct a thorough risk assessment, to see where our explosion hazards may come from. This is because some equipment can only detect one type of gas or substance, as mentioned earlier. The hazardous substances may also only be in certain locations at certain times, so if we test at the wrong time, we will get the wrong picture of what is going on. Another weapon at our disposal is ATEX equipment.
ATEX equipment
ATEX equipment is equipment that, due to its design, is “explosion proof”. ATEX equipment is usually easy to spot, as it will have a special symbol on it. This symbol is a hexagon, with the phrase “Ex” within it. Unless ATEX equipment is faulty or damaged, it should be close to impossible for it to be the ignition/heat source for a fire/explosion. As always, bear in mind that even safety equipment can fail, so always be vigilant. “Explosion Proof” does not mean you can strap a stick of dynamite to it, and it would survive (cue ACME incorporated and Wil.E.Coyote for your older readers).
ATEX equipment can be almost anything, depending on your needs. Indeed, some of the gas detection equipment we discussed earlier in the article would be classed as ATEX. Some other examples include:
- Lighting – LED bulbs rather than glass (less energy used, do not get as hot), impact resistant covers and materials, over-temp protection, fully sealed housing to prevent entry of flammable substances
- Hot-work habitats – fully sealed and pressurised to allow safe welding, grinding and other sparkproducing activities
- Atmospheric measurement – we discussed gas testing and monitoring earlier in the article
- Pneumatic equipment – uses air instead of electricity as the power source, eliminating cables, plugs and other electrical hazards
There are a plethora of specialist companies and suppliers out there who design, manufacture and train people on this equipment. So they would have a wealth of knowledge and expertise available to you, if you are not sure what is the best solution for your own circumstances.
Should it all go wrong, as always, we should have some sort of emergency plans and procedures in place. This is vitally important with any fire and/or explosion, as unlike some incidents, the situation can escalate dramatically within an incredibly short time.
Breathing apparatus
As part of this plan, something you could issue your workers is the use of BA, otherwise known as breathing apparatus. Whilst using this equipment would not prevent the fire and/or explosion occurring in the first place, it would be a vital mitigation tool in giving our workers a fighting chance of getting out of the situation alive. Indeed, depending upon certain legal requirements (such as regulations surrounding hazardous zoning, working in confined spaces, working with certain hazardous substances, and so on) you may not be allowed to enter the work area unless you are wearing this equipment anyway.
BA can come in three types. These are: Fresh Air Hose systems, SABA (Supplied Air Breathing Apparatus) and SCBA (Self-Contained Breathing Apparatus). The main types you would find in the workplace would be the latter two. The application I usually associate with the first one is snorkelling, where the user draws air through the hose, and expels it through the same hose. Unfortunately, this type of application would have limited use in most workplaces where fire/explosion hazards could occur. This is because the worker would simply breathe in the smoke and other harmful contaminants through the unfiltered hose.
“emergency plans are vitally important in any fire and/or explosion as the situation can escalate dramatically within an incredibly short time”
By comparison, SABA would consist of a worker wearing a full-face mask, connected to an air-hose, that is then connected to a permanent air-supply (e.g., a bank of air-compressors on part of the site). The drawback with these systems is the fact that the workers would have to disconnect themselves from the fixed hose, and have an SCBA or other Emergency BA system to use, to continue to have a fresh source of air in order to escape safely. The hoses themselves could present a trip or fall hazard should they be left scattered on the floor, or not retract into their reels/ holding systems in an emergency. SCBA would negate this issue, as the air would be supplied by a tank on the wearer’s back, eliminating any hose issues mentioned previously.
There are some drawbacks, however. The main one being that there is only a limited amount of air to breathe before the wearer runs out (for example, most SCUBA Divers would get 25-30 minutes from a standard air tank on a normal dive). Another drawback is that this equipment can also be quite bulky and heavy, which could hinder workers during their attempts to escape.
Ultimately, by having this equipment as part of our plan, we can be confident that we limit the chances of any workers becoming victims of the biggest killer of a fire, inhalation of smoke and other contaminants.
Preventing build-up
The best-case scenario would be to prevent the build-up of the flammable substance in the first place, by eliminating, if not reducing, the hazard. This can be done through using minimal amounts of the substance (if any at all) for our work, or “purging” work areas with non-flammable materials before hot work and other activities are done (such as flushing pipes with nitrogen, or pigging – cleaning the interior of pipes with specialist equipment). Good maintenance of piping, tanks, storage vessels, or anything that would contain a hazardous substance is another tactic that would greatly benefit us, as this would prevent unnecessary leaks and releases of hazardous substances caused by corrosion, holes, broken seals, and so on.
Good control of ignition and heat sources is also something to look at. Do you employ a permit-to-work system? Are workers informed of areas where they can smoke on site (if at all)? Have you even considered out-sourcing some, or all, of your hot works to an outside contractor to perform it on their site? Fire-fighting measures are something else to look at. It could be simply a “fire-watcher” standing by with a fire extinguisher, immediately extinguishing any sparks produced by the activity, or wetting-down hot areas as a precaution. Of course, if you work on a process facility, there may be much more technical measures in place. These would include emergency shutdown systems, pressure release and/or containment valves and systems (depending on the scenario), automated fire-fighting systems such as “water birds”, or even your own emergency response and firefighting teams and departments.
Conclusion
Do not forget, that it is always important to liaise, co-operate and co-ordinate with your contractors, local authorities and emergency services in the case of fire and/or explosion incidents (perhaps you could conduct joint drills, for example). Also, bear in mind that flames and smoke are not the only threat from working in explosive atmospheres. How are you going to deal with people who are trapped in an area? Have you deployed blast-proof materials in the design and construction of your facilities/ equipment? How many escape routes and assembly/muster points do you have, and are they in “places of safety”? I remember working on a few sites where not only did we have to meet at a Muster Points, we would then have to be evacuated by busses and other vehicles a large distance from site (in one case five kilometres!).
Working in explosive atmospheres inherently has risk, simply due to the nature of the substances we are working with. Managed well, however, you can ensure you are not “blown-away”.
