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Types of Gas Hazard: What You Need to Know

Types of Gas Hazard: What You Need to Know

Posted by Claire Allcock on 7th Feb 2020

Getting your gas detection system right stems from understanding the types of hazards that gases can create in your workspace. There are three main gas hazards to know about, with different considerations for each. It’s important to note that some gases can fall into two categories, so make sure you fully understand the gases you need to monitor in your environment!

Flammable Gas Hazards

Also known as fuel gases, flammable gases increase the risk of fires or explosions. Ammonia, hydrogen, and propane are all flammable gases.

The Fire Triangle

For a fire to occur, you need a source of ignition, oxygen, and fuel — the flammable gas acts as the fuel in this case. The core principle of fire protection systems aims to remove at least one of these three elements to the triangle to prevent a fire.

Flammable Gas Ranges

The flammable range for each gas falls into a band of gas to air concentration, between the UEL (upper explosive limit) and the LEL (lower explosive limit). Below the LEL, the concentration of flammable gas is too low to be used as fuel in the fire triangle. Above the UEL, the concentration of flammable gas is too high, meaning there isn’t enough oxygen in the atmosphere to produce a fire.

The flammability range of a gas can be increased by increasing the pressure, temperature or oxygen content in the atmosphere.

Safety & Detection

The average industrial plant should have no gas leaking into surrounding areas of the environment, so the detection and early warning system would only be required to detect levels from 0% up to the LEL.

Typically, a safety margin of concentrations of less than 50% of the LEL is used in detection systems. In enclosed or unventilated environments, a gas concentration greater than the UEL may occur; in these instances, workers must be careful when opening hatches or doors, as they may introduce more oxygen into the atmosphere and bring the concentration into the flammable range.

Flame detectors are also a great line of defence for your workplace, using multiple spectrums of light to ensure accurate detection.

Toxic Gas Hazards

Toxic gases carry the risk of poisoning if inhaled, ingested or absorbed through the skin. Some examples of toxic gases include carbon monoxide, chlorine, and nitrogen dioxide.

Risks of Toxic Gases

Toxic gases are extremely dangerous; some gases can be poisonous at very low concentrations, and more fatalities occur from toxic gas exposure than from explosions of flammable gas. Toxic gases can also cause adverse effects from additive, long-term exposure, highlighting the importance of measuring total exposure time as well as gas concentrations.

While some toxic gases have strong smells like the recognisable ‘rotten eggs’ smell of Hydrogen Sulfide, others are odourless and undetectable by humans.

It’s important to note that some gases can be both toxic and flammable; they are usually treated as separate hazards due to different regulations and sensors needed.

Safety & Detection

While the obvious focus for concern is on the Health and Safety of workers, toxic gases also have the potential to contaminate manufactured end-products. This then leads to disruptions to production lines and normal working processes.

Monitoring the workplace as well as workers by integrating fixed and portable gas detectors into the overall safety plan are the best practices. To cover every eventuality, detection instruments should also monitor short and long term exposure levels, as well as instant alarms for dangerous concentrations.

Asphyxiant Gas Hazards

Asphyxiant gases are non-toxic or minimally toxic and reduce or displace the normal concentration of oxygen in breathing air. Argon, helium, and butane are all examples of asphyxiant gases.

Oxygen Deficiency

Normal ambient air has an oxygen concentration of 20.9% v/v. The atmosphere is classed as oxygen-deficient at concentrations below 19.5% v/v. Oxygen depletion can be caused by displacement, combustion, oxidation, chemical reaction or bacterial action.

Deficiency isn’t the only hazard in the workplace. Oxygen enrichment can also be dangerous, as increased oxygen levels raise the flammability of materials and gases. At levels of 24% v/v, clothes can spontaneously combust.

Safety & Detection

Aspyxiants work by displacing so much oxygen from the ambient atmosphere that the haemoglobin in the blood cannot pick up enough oxygen from the lungs to fully oxygenate the tissues. As a result, the victim slowly suffocates, which can lead to death.

The only way to detect oxygen levels is with real-time monitoring of continuous oxygen depletion sensors.

Installing the right gas safety systems can only be achieved from having a deep understanding of the risks in your environment, with knowledge of what gases you need to monitor to keep your workforce safe.