We don’t think much about air. It’s kind of like the police; you don’t think of it much until you desperately need it. The air, assuming you are breathing ambient atmosphere, contains in each breath 78% nitrogen and 21% oxygen, along with what the greatest scientific minds on Earth refer to as “other stuff”.

This “other stuff” mostly comprises gases including carbon dioxide, neon, hydrogen – and methane if the person next to you had baked beans and boiled cabbage for dinner last night – but also aerosols, which are tiny particles that float on air and that we can breathe into our lungs. Some of these particles, for example dust and pollen, are picked up naturally when the wind blows, but even these are far from harmless, particularly if one has a respiratory condition like emphysema, asthma, or COPD. Worse still, air can carry particles that are created by, or used in, the industrial processes like soot, smoke, asbestos, silica, coal dust, and even some extremely dangerous and potentially lethal gases.

Hierarchy of Controls

“Sometimes, all that I need is the air that I breathe and to love you” The Hollies

So how do you know the contents of the air that you breathe (I assume that is why the Hollies qualified its statement with “sometimes” because all the love in the world isn’t going to sustain you if you are breathing in Zyklon B gas). Fortunately, there is a multi-pronged defence system based on the Hierarchy of Controls.


Many chemicals once thought to be safe have since been banned once it was discovered that said chemicals had an adverse effect on people, animals, or the environment. DDT, the once ubiquitous pesticide, was banned by most industrialised countries when it drove some animals to the brink of extinction and is suspected of being a human carcinogen. I grew up on a farm in the good old days of DDT and we never saw birds other than starlings and sparrows nor any other wildlife except large mutant groundhogs so ornery that they would routinely beat me up for my lunch money. Now the area owned by my simpleton younger brother is teeming with wildlife – from the raccoon (let’s face it, they’re trash pandas and we all know it) to majestic bald eagles. On a side note, the bald eagle found out very readily that the once endangered and now perpetual pest the flying rat, or the tern as it prefers to be called, was easy pickings. One day I visited my brother and in a matter of days a bald eagle had killed and eaten 200 or so of the nuisance birds (the flock numbered more than a thousand but the survivors decided that, what with discretion being the greater part of valour, to move on.)

“the greatest challenge associated with protecting workers from air-borne hazards is understanding the exact composition of the ambient air”

There are literally hundreds of examples of banning the use of harmful chemicals with which I could bore you, but let’s face it, I am too lazy to do the research.


Probably the most widely known example of substitution is the advent of unleaded petrol. Lead, widely known for its myriad health hazards, was expelled into the atmosphere as a by-product of the combustion process used to power automobiles and other vehicles.

I have always found something extortive in selling unleaded gas at a higher price than regular gas. I mean, are they seriously going to sell me something at a premium for not putting a poison in it?!? I hope restaurants never get this idea. “Did you want the cook to spit in your food? No? Then I will have to charge you extra! This approach to sales in marketing is just addle-headed and wrong.

Engineering controls, administrative controls, and PPE

Engineering controls are used in many cases to prevent the harmful gases from entering the areas where workers might be exposed, and I will do my best to keep this simple, but I honestly think that when it comes to atmospheric hazards it is tough to treat these lower controls as one discrete element because these three types of controls so often work so closely together: from engineering controls like ventilation systems, to administrative controls like warning placards, to Personal Protective Equipment (PPE) like Self-Contained Breathing Apparatus (SCBAs) – no single control is typically enough to provide adequate protection from a poisonous atmosphere.


Perhaps the greatest challenge associated with protecting workers from air-borne hazards is understanding the exact composition of the ambient air. Okay, now for a little primary school science. We need to do more than just breath to stay alive (respirationally speaking) we need oxygen in sufficient quantities to live (unless somewhere somehow a plant is reading this, in which case, how cool is that?). So, the first complication is how much air is in the area in which a worker is working? That is relatively easy if you paid attention in Geometry class, which I did not. I mean talk about the cards being stacked against you! I can’t prove Pythagoras’ theorem and I’m wrong? Seriously why do we all tip-toe around this dead Greek guy? Maybe HE’S wrong, maybe his theorem was complete dreck and people now are just afraid that if they say that his work is rubbish they will be ridiculed. I say “screw Pythagoras and Euclid too for that matter!” My Geometry teacher, Sister Ceilia, was a wonderful person and while kind, had kind of a stubborn streak – to the point where she would mark my answers incorrect, when I would respond to the problem: Prove Pythagoras’ Theorem with “I think we should just take Pythagoras’ word for this on this one sister.”

“incorrect gas sensor positioning will result in an ineffective gas detection system”

Since umpteen mathematicians have conspired to keep Pythagoras’ dirty little secret, isn’t my answer both technically, literally, and allegorically correct? Any way I miraculously passed geometry, owing largely to what would later be known as “social promotion” (weasel speak for pass the trash) although my situation was probably better described as anti-social promotion. On a sort of related note, I made a plea bargain with my university professor wherein I would receive a passing grade in calculus in exchange that I never take a maths class again.

Anyway… calculating the amount of air in a room is the only useful application of mathematics currently known to man.

According to https://www.creoven.co.uk/calculation-of-air-volume first you must calculate the volume of the workspace using the formula “length(m) x width(m) x height(m)” The result of this calculation only tells you how much air can be contained in this space, but the purpose of the room and the amount of activity need to be considered to calculate the air change rate (ACH).” All this means is that a workspace (which they assume is cube shaped and that is not always the case) can only hold so much air. But if people are going to be working in the area the air will be consumed unless there is proper ventilation which can be an exhaust fan, an open door or window, or air pumped into the room.

People also pollute the air (back to that cabbage and baked beans your co-worker ate). We exhale “78% nitrogen, 16% oxygen, 4% carbon dioxide and 0.09% argon. Some scientists suggest that exhaled breath contains as many as 3,500 compounds, most of which are in microscopic amounts”1 So while it is true that simply by breathing we are using up oxygen in small amounts a large group of people in an enclosed space; well at least that is as long as all they are doing is breathing. Sometimes environmental factors contribute to the exhaustion of oxygen.

“incorrect gas sensor positioning will result in an ineffective gas detection system”

Any source of combustion consumes oxygen and increases the presence of exhaust gases. Some gases that are exhausted displace oxygen and make it harder to breath. Carbon monoxide is a particularly hazardous and common threat. “Carbon monoxide is attracted to haemoglobin in the bloodstream. This means, when you inhale CO gas, it replaces the oxygen in your blood that all cells in your body need to function. As you continue to breathe polluted air, carbon monoxide rapidly accumulates in your system and symptoms of low oxygen begin to show up. When this happens, you’re considered to have carbon monoxide poisoning.

Some of the most common symptoms of CO exposure are flu-like symptoms. In fact, of the 12,000 patients admitted to the hospital with flu-like symptoms each year, about 2,000 are thought to actually be suffering from CO exposure.

In all, the common symptoms that point to carbon monoxide poisoning include:

  • Headache
  • Fatigue
  • Sore throat
  • Dizzy spells
  • Rapid heart rate
  • Memory loss
  • Difficulty concentrating
  • Confusion and irritability
  • Sensitivity to light, sound and odours
  • Nausea and vomiting
  • Loss of consciousness
  • Brain damage
  • Death2

On the other hand, lethal carbon monoxide poisoning tends to leave a great looking corpse so I guess that it is, like so many things in life, a matter of priorities.

Fortunately, there are a lot of great companies out there who make it relatively easy to determine whether or not the air we breathe contains hazardous or poisonous gases. Gas detectors and monitors are available in two basic forms: stationary and mobile.

Stationary gas detectors

Stationary gas detectors are fixed in one position, typically where one would likely expect hazardous gases to accumulate.

“Incorrect gas sensor positioning will result in an ineffective gas detection system. Firstly, it won’t protect those who work there and secondly, it won’t protect the workplace.

The benefit of installing a gas detection system is to detect dangerous concentrations of hazardous gas. Once set levels are met, the system has the capability to trigger alarms and activate countermeasures such as fan control systems. However, this can only be achieved if the gas sensors have been positioned accurately.

“my monitor screamed like a banshee, I calmly checked the windsock, proceeded cross-wind to safety”

Leak source

The optimum method of gas detection is to place the gas sensors as close as possible to a potential gas leak source. Leaks are most likely to arise from pumps, valves, flanges, joints and shut-off devices.

If such locations cannot be easily identified, gas sensors need to be installed over the entire hazardous area. It is essential that the target gas can always reach the gas sensor at operational conditions within a realistic time interval.

Weight of gas

The most common flammable gases which are considerably lighter than air: Hydrogen (H2), Ammonia (NH3), and Methane (CH4). Sensors for these gases should be mounted at a high level.

Heavier than air gases: Butane (C4H10) and Sulphur Dioxide (SO2), and vapours of flammable liquids require gas sensors to be installed at
a low level as they flow downwards, as long as they are not disturbed by air convection.


Considerations must be paid to process conditions. If gas is released under pressure or high temperature, gas may rise rather than fall.

Air currents

Natural or forced air currents may cause gas to behave differently. Gas sensors should be positioned in ventilation ducts if appropriate.


Gas sensors should be installed pointing downwards to prevent dust and water collecting and entering the gas sensor.

When mounting gas detectors outside, consider the possible damage caused by rain or flooding. Splash-proof weather guards will protect gas sensors to a degree, but gas sensor positioning must be considered for potential large volumes of water.

Use a gas detector sunshade if locating a gas detector in a hot climate and in direct sun.

Gas sensor orientation

Some gas sensors must be positioned using a certain orientation. The catalytic bead sensor must be installed vertically with the gas sensor pointing towards the ground. If the gas sensor is not mounted in this way, then the gas sensor may not work correctly.


When fitting open path IR devices, it is important to ensure that there are no potential obstacles blocking the IR beam.

Before any wiring is laid, consider the length of cabling required and the obstacles that need to be avoided between the gas sensor head gas controller and building management systems. We can overcome this with the introduction of wireless communications.

Service and calibration

Consider ease of access for service and calibration. Gas sensors that are positioned high may require a temporary platform or ladder for access which can increase service visit time and costs.3

Mobile gas detectors

While stationary gas detectors are an important source of protection against harmful gases, while the detectors remain stationary gases don’t necessarily follow suit. My life was saved by a wearable gas detector. Once while doing a safety culture intervention, one of the brain trust that was working at the facility decided to vent hydrogen sulphide as my facility guide and I stood above the exhaust vent. My monitor screamed like a banshee awoken by the rubbish collector after a three-day bender. I calmly checked the windsock, proceeded cross-wind to safety in the course of about five seconds. I learned this procedure after watching a safety video before entering the facility. Before that I didn’t have much use for safety orientations and had NO use whatsoever for safety videos. I was wrong; get used to it. Nothing like a near death experience to change your world view.

Wearable monitors are versatile but typically not all purpose. Consult your Safety Data Sheet and a reputable vendor before selecting a mobile detector.

Top considerations

Portable gas detection monitors represent a critical safety component used in many industries to protect employees, people in nearby areas, and the environment in the event of a noxious gas leak. Gas leaks can happen at any time, and the best way to prevent adverse effects is to recognise leaks and mitigate them as quickly as possible. Therefore, a portable gas leak detector can be the first line of defence in preserving the well-being of all nearby life and protecting nearby property.

While there are many portable gas detectors on the market, not all of them are suited to your circumstances and needs. For example, if you’re only concerned with low oxygen environments, you won’t want to purchase a portable multi gas detector. However, if there are leak risks from multiple gases in a manufacturing environment, a portable multi gas detector may be the perfect tool for your situation. When you begin your search for the right portable gas detector for sale, there are some things you should consider before making a purchase. Read on to learn about a few of the top considerations you should take into account when shopping for a portable gas detector.


Accuracy is of the utmost importance when it comes to portable gas detectors. You want a detector that can accurately measure the presence of gases on your worksite and relay that data in real time. Accuracy, in general, means that the detector can provide measurements that closely resemble the actual concentrations of gases on your site. Good accuracy can be described as readings that are within 5% of the actual concentration of gases present in the work area. Also, sensitivity is a part of accuracy, as you need the detector to measure the presence of gases that are at least equal to the minimum allowable limits.


An overly complicated gas detector could be problematic if your operators don’t want to use it or don’t feel comfortable using it. Put yourselves in the shoes of employees who will be using the monitor. If the portable monitor is to be carried all day, would you rather it be heavy or light? Should it be awkward and cumbersome or streamlined and highly portable? Would you rather have a bright display and loud audible alarms or more subtle alert features? Are data displays easy to read and interpret? These are all factors you should consider when selecting a detector.


Cross-sensitivity describes the probability of your detector picking up gases that may confuse it or slow down accurate measurement of the target gas. For example, readings of a target gas could be skewed by the presence of an off gas, which could lead employees to assume the detector has malfunctioned or to ignore readings that appear falsely elevated. Check the cross-sensitivities of the detectors you’re considering and make sure you understand how they can impact readings in a work environment.

Response time

When you work with potentially dangerous gases, the response time of your detectors is critical. Time can mean the difference between life and death, and in a dangerous situation involving toxic gases, even a few moments can be important in preserving life. Look for detectors with an extremely fast response time. The onset of physical symptoms of exposure to some gases can begin in as little as 30 seconds, so you need a detector that can measure and display data within 15 seconds.


A gas detector that can’t be relied upon is almost as dangerous as not having a monitor at all. Because of the nature of the task they perform, you want a reliable gas detector that you can trust to alert you to potentially dangerous situations in the workplace. Only consider detectors from trusted manufacturers that are bolstered by positive reviews. Pay particular attention to information regarding the durability of a detector under consideration. It should perform regardless of weather conditions, temperatures, relative humidity, and air pressure.4

1   https://sciencing.com/chemical-composition-exhaled-air-human-lungs-11795.html
2   https://www.aireserv.com/about/blog/2016/october/why-is-carbon-monoxide-so-dangerous-/
3   https://bit.ly/3fKxb7N
4   https://tinyurl.com/j8hx28jd