Why do I need a Gas Detector?


From the dawn of time, nature has had invisible ways of causing hazards for mankind, dangerous gases that can harm or kill humans can be found in a variety of locations from volcanoes to mine shafts, but without educating people on the dangers of these gases, humans will continue to fall foul of the dangers.


The air around us consists of roughly 78% Nitrogen (N), 21% Oxygen (O2), and 1% various other gases. If the oxygen concentration around us becomes depleted this can have disastrous effects on the body that may result in death. Nitrogen is a naturally occurring gas that is also used by industry in pure form to purge areas of explosive gases and reduce or remove explosive hazards. Other gases that may be found in a natural setting can be methane (CH4 an explosive gas) Hydrogen Sulfide (H2S flammable, poisonous, smells of rotten eggs), and Carbon Monoxide (CO byproduct of combustion will attach to hemoglobin in blood to prevent the bodies take up of Oxygen)


How do we know what is in the atmosphere around us?

Without some form of detection, it is very difficult to ascertain what we are breathing, in non-industrial settings, from the office to the park, we assume that the air is safe to breathe. Most of the time that assumption is correct. Once we move into an industrial or underground setting, the atmosphere around us can change rapidly without our noses detecting the dangers. Every year many deaths occur in confined spaces where people enter a hazardous atmosphere due to a lack of understanding of the dangers. Some of these are not in industrial settings.


In 2013 a father and 2 sons died on a farm in Northern Ireland after being overcome by gas and drowning in a slurry tank. These tragedies can be prevented by educating people to the dangers and providing adequate protection and equipment where required.


An “off the shelf” gas detector will usually be set to detect 4 gases and their levels in the air around the user.


Explosive gas sensor LELs (Lower Explosive Limit)

Carbon Monoxide

Hydrogen sulphide


When will the monitor alert you?

The detector will be set to go into alarm for different reasons;

Oxygen sensors will be set to detect the “volume in air” (VIA) usually set to alarm around 19.5%VIA for a low reading and 23%VIA for a high reading. Low oxygen is obviously dangerous as we need oxygen to survive, high oxygen levels increase the risk of fire or explosion. High oxygen levels can only be a man-made problem, leaking cylinders for example.


LEL (explosive gases) sensor is designed to detect an explosive atmosphere, dependent on the nature of the gas will determine how quickly the alarm activates. Acetylene and Hydrogen are extremely explosive gases and will only require a small amount to cause an environment to become explosive, naturally occurring explosive gases like methane will also activate the LEL sensor dependant levels in the atmosphere.

Carbon Monoxide sensor is set to detect in Parts per Million of an atmosphere (PPM) device will usually be set to alarm at 25ppm to give the user sufficient warning that the environment may be getting dangerous.


Hydrogen sulphide is another naturally occurring gas that will set off gas detection systems at around 10ppm. If this gas is inhaled in large amounts it will disable the sense of smell and lead to death by pulmonary edema.


A variety of equipment can be purchased for the purpose of personal gas detection, advice should be sought if you are unsure of the hazards that you face in your workplace.


For more assistance contact the team at QAB