TALKING Gas

Welcome to Talking Gas

Get to know your gases with the
experts at Crowcon

Making the world a safer place

Crowcon has a wealth of knowledge regarding gas detection technologies and applications, gained over many installations around the world – and we’re keen to share that knowledge!

Our “Talking GAS” resource hub is intended to help and provide those dealing with gas hazards with a sound understanding of gas sensor technologies, gas properties and detection techniques.

We’re aiming to help you strengthen hazard management at work. However, you should of course always undertake a full site specific assessment for workplace risks!

Our Talking GAS factsheets are coming soon. Below you will find a number of other important resources to help you understand and manage gas detection in the workplace.

Key gas detection resources

What is gas?

The name gas comes from the word chaos, which neatly summarises the main feature of the simplest state of matter.

A gas is a swarm of particles moving randomly and chaotically, constantly colliding with each other and the walls of any container. The real volume of the particles is minute compared to the total space which they occupy and this is why gases fill any available volume and are readily compressed. The average speeds of gas molecules are of the order of 100s of metres per second and they are colliding with each other billions of times per second. This is why gases mix rapidly and why they exert pressure.

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Flammable Risk

In order for gas to ignite there must be an ignition source, typically a spark (or flame or hot surface) and oxygen.

For ignition to take place the concentration of gas or vapour in air must be at a level such that the ‘fuel’ and oxygen can react chemically. The power of the explosion depends on the ‘fuel’ and its concentration in the atmosphere. The relationship between fuel/air/ignition is illustrated in the ‘fire triangle’.

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Combustion of gases and vapours

Most organic chemical compounds will burn. Burning is a simple chemical reaction in which oxygen from the atmosphere reacts rapidly with a substance, producing heat.

The simplest organic compounds are those known as hydrocarbons and these are the main constituents of crude oil/gas.

These compounds are composed of carbon and hydrogen, the simplest hydrocarbon being methane, each molecule of which consists of one carbon atom and four hydrogen atoms.

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Flammable gas characteristics

Flammable liquids generally have a low flash point. This is the temperature above which vapour is given off at sufficient rate to form an explosive mixture with air.

Liquids with flash points below normal ambient temperatures automatically release vapour in sufficient volume to provide an explosive mixture; thus leakage of such liquids is potentially as dangerous as a flammable gas leak.

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Toxic Risk

Gases and vapours produced, under many circumstances, have harmful effects on workers exposed to them by inhalation, being absorbed through the skin, or swallowed.

Many toxic substances are dangerous to health in concentrations as little as 1ppm (parts per million). Given that 10,000ppm is equivalent to 1% volume of any space, it can be seen that an extremely low concentration of some toxic gases can present a hazard to health.

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Monitoring for toxic gases

Chemicals, fumes, dusts and fibres can under many circumstances have harmful effects to workers exposed to them by inhalation, being absorbed through the skin, or swallowed.

Persons exposed to harmful substances may develop illnesses (for example; cancer) many years after the first exposure. Many toxic substances are dangerous to health in concentrations as little as 1ppm (parts per million).

Given that 10,000ppm is equivalent to 1% volume of any space, it can be seen that an extremely low concentration of some toxic gases can present a hazard to health.

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Toxic gas exposure limits and alarm levels

It is important to note that whereas portable gas detection instruments measure and alarm at the TWA levels, instantaneous alarms are included to provide early warning of an exposure to dangerous gas concentrations.

Workers are often under risk of gas exposure in situations where atmospheres cannot be controlled, such as in confined space entry applications where alarming at TWA values would be inappropriate.

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Characteristics of toxic gases

To understand the impact of toxic gases, it is important to familiarise oneself with the relative density to air, formula and characteristics of such gases.

This table explains the characteristics of 25 different toxic gases commonly encountered in the workplace.

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Oxygen Risk

The normal concentration of oxygen in the atmosphere is approximately 20.9% volume. Oxygen levels can be dangerous if they are too low (oxygen depletion) or too high (oxygen enrichment).

The same oxygen monitor will alert to both enrichment and depletion. In the absence of adequate ventilation the level of oxygen can be reduced surprisingly quickly by breathing and combustion processes.

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Installing Fixed Gas Detection Systems

The normal concentration of oxygen in the atmosphere is approximately 20.9% volume. Oxygen levels can be dangerous if they are too low (oxygen depletion) or too high (oxygen enrichment).

The same oxygen monitor will alert to both enrichment and depletion. In the absence of adequate ventilation the level of oxygen can be reduced surprisingly quickly by breathing and combustion processes.

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Why consider moving to an addressable fixed gas detection system?

Conventional analogue ‘point to point systems have been around for many years and for many gas detection operators, is still their first choice. 

Using a gas detection system that has familiar technology and functionality benefit a busy operator and provide a level of peace of mind.

However, the traditional analogue system does have its limitations, including each detector needing its own individual cable connected to the central control panel.

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What is LEL?

The Lower Explosive Limit (LEL) is the lowest concentration of a gas or vapour that will burn in air.

The Lower Explosive Limit (LEL) varies from gas to gas, but for most flammable gases it is less than 5% by volume.

This means that it takes a relatively low concentration of gas or vapour to produce a high risk of explosion.

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Find the right gas detector

What gas do you need to detect?

Choose the type of detector and the type of gas below

Single or multi-gas monitors

Can be used for personal monitoring and portable safety applications

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Fixed gas detectors

Are effective as they can be integrated with ventilation control systems

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Control panels

Measure and report the presence of dangerous levels of chlorine and activate alarms/associated equipment

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