Gas! Gas! Quick, boys!
Left unchecked, gases found in confined spaces have proven time and again to cause fatalities and injuries. SHEQ MANAGEMENT uncovers a witch’s cauldron for the brewing of life-threatening gases.
Imagine taking a dozen balloons to an open field and filling them with gases that are heavier and lighter than air respectively. Upon release into their natural habitat, the balloons with lighter than air gases should drift up and away, while those containing the heavier than air gases bumble along on the field’s surface.
Now, picture these same balloons inside your living room. The balloons with lighter than air gas will collect at the highest point or corner of the room, while the heavier than air balloons group together at the lowest point.
Remember that there are no environmental variations (such as wind temperature) inside your living room. So, if left alone, these balloons will remain exactly where they are – at the very top or bottom of the room. Open a door, however, and they become disturbed. In a nutshell, this is what happens to gases in work-based confined spaces.
According to Bob Henderson, president of Good for Gas (GFG), one of this year’s Noshcon speakers, “Confined spaces are large enough for worker entry, but not designed for continuous occupancy. Furthermore, they have limited openings for entry and exit. Examples would include septic tanks, drain pipes, degreasers, and even mines are a veritable witch’s cauldron for brewing life-threatening gases.”
What is perhaps most important is the fact that confined spaces aren’t permanently occupied. This means that they are sometimes left unchecked, allowing for various toxic and combustible gases to build up.
Whereas gases such as butane are given a chemical additive for home use to be noticeable by smell, many gases are in fact odourless. Therefore special measures always need to be taken by workers entering confined spaces to ensure correct safety protocols.
With opening and closing of confined spaces being a necessary part of the work environment, each time someone crawls down a pipe or opens up a hatch somewhere, a moment of risk is created which includes a high probability of exposure to any number of gases that could poison, suffocate, or set the worker on fire.
Wherever some sort of combustion takes place within an enclosed space, one can be sure that carbon monoxide will be present. Where there is biological waste – for example, a drain pipe or sewer – methane gas will build up in a pocket at the top of the enclosed entrance. Considering that entryways and hatches into many confined spaces will create a pocket in which gas can collect, employees face a lethal threat that is quite literally on the other side of a door.
In days gone by, firedamp and blackdamp at mines were one of the biggest causes of loss of life, due to the fact that they could not be seen and were odourless. Without a miner’s canary or Davy lamp, the dangerous gases would only be noticed the moment workers started dropping – most often too late. It should be noted that canaries were still used in mines in the United Kingdom as recently as 1986, when they were replaced by gas detectors.
Today, gas detectors come in various configurations and are made for a plethora of industries. For toxic gases such as firedamp, electrochemical sensors, or cells, are usually used. These function via electrodes that signal when a specific gas is detected.
To detect combustible gases such as methane, either catalytic sensors or infrared (IR) detectors are utilised. IR detectors detect gases when they interfere with the power of light transmission between the IR detectors’ transmitter and receiver.
But, despite these technologies, several threats still go unnoticed. For example, when other gases start filling up a confined space, the percentage of oxygen contained in such a space is reduced. As oxygen is what keeps human metabolism going, it is a vital gas for survival.
According to Henderson: “An oxygen percentage of less than 19,5 percent is considered to be oxygen deficient and therefore detrimental to human health and safety. But sometimes we forget that a percentage is not the only variable one has to factor into the equation.
“Although the percentage of oxygen at the top of Mount Everest is the same as that at sea level, this does not mean that it is as breathable. As the altitude increases, air density decreases and so does breathability. This means that confined spaces in higher altitudes need to practice effective gas detection, and also compensate for the thinner air.”
Therefore, checking the height of a confined space is essential. Luckily there are quite a few helpful websites with information on gas detection, practice and safety implementation.