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The environment and gas risks

The environment and gas risks

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When we talk about gas risks in the environment, we often think of "natural" gas and the risks associated with managing this fossil fuel. In our case, gas risks are not limited solely to this application, but to a large number of activities, particularly in the environmental sector. In this article, we will focus on gas risks and the precautions to be taken by operators who work on a daily basis to manage drinking water, waste water and waste management.

To find out more, come and meet us at the Pollutec exhibition from 10 to 13 October. We'll be on booth H5-D063 to raise awareness and protect the many people working to promote sustainable development and protect our environment from gas risks.


Definition: environment, gas

BE ATEX gas guide
BE ATEX gas guide

According to the dictionary, the word environment means "that which surrounds us". Gas means a set of atoms or molecules that are very weakly bonded and virtually independent, and that tend to occupy an entire available volume in a gaseous state: it is therefore found everywhere and all around us. In conclusion, gas is part of our everyday environment.

There are different types of gas. Each of them presents different types of risk that can be protected against. Upstream, using certain types of equipment to detect it; or downstream, to protect yourself when gas is released (respiratory protection equipment) or to ensure safe access (equipment to prevent the risk of falling from a height). From waste recycling to wastewater treatment, from industrial risk prevention to the protection of biodiversity, gas and its risks are omnipresent.

Gas risks

Flammable gases
(methane, butane, propane, etc.)
Explosion or fire risks
Toxic gases
(Carbon monoxide, hydrogen sulphide, carbon dioxide, chlorine...)
Intoxication and poisoning
Gas inducing oxygen consumption or vice versa

Anoxia and hyperoxia

To find out more about the characteristics of the different types of gas, please consult our gas guide:

Environment: gas risks in water management

Drinking water management

Drinking water

By definition, water is a liquid body, colourless, odourless and tasteless at ordinary temperature and pressure. It is composed of one oxygen atom and two hydrogen atoms: H₂O.

Without water, there would be no life on Earth. In fact, 65% of our bodies are made up of water, which is essential for our existence. We use it every day for drinking, washing, watering the fields in agriculture as well as in numerous industrial applications... Water management is a strategic issue for our future!

Water is a seemingly harmless part of everyday life, but there are many risks involved in managing it: gas risks (see table above) and the risk of falling from a height.

Water management professions work in an environment that is often damp and dirty. To ensure that the water reaches us in a drinkable state, the pipes have to be cleaned and checked. To do this, workers enter narrow spaces, commonly known as confined spaces. Entering a confined space is highly regulated, requiring training as well as a certain type of equipment to protect operators: a 4-gas detector (for O₂, CO, H₂S and CH₄), a tripod, a harness and a self-rescuer.

For more information:

Wastewater management

Water treatment plant

Water has become a scarce resource. The climate change we have been experiencing in recent years is making us increasingly aware of water management issues. The treatment of wastewater is becoming a process that we are seeking to exploit, and a number of businesses are developing around biogas.

Wastewater is treated in wastewater treatment plants. The gases generally monitored are oxygen (O₂), hydrogen sulphide (H₂S) and methane (CH₄). Added to these are new gases linked to purifying products for cleaning and decontaminating wastewater or for eliminating micro-organisms from clean water.

  •     Chlorine (Cl₂) to sterilise drinking water. In the presence of turpentine or ammonia, it is highly flammable.
  •     Ammonia (NH₃), present in waste water (urine, cleaning chemicals etc ...), it can be dangerous in copper piping and cause significant corrosion. It is highly toxic during the handling and drying of sludge.
  •     Chlorine dioxide (ClO₂), an oxidising gas used to disinfect drinking water. It kills bacteria, viruses and fungi.
  •     Ozone (O₃), a very harmful gas resulting from chemical reactions during water treatment.

For more information:

Recovering wastewater: biogas

biogas plant

Wastewater sludge is transferred to anaerobic digesters to be mixed with micro-organisms. The latter further decompose the sludge into biogas, which has a high methane (CH₄), carbon dioxide (CO₂) and hydrogen sulphide H₂S (3000ppm) content.

This biogas is now recovered: it must be treated in order to be used as an energy source. This is what is known as green energy or clean energy.

BE ATEX offers the expertise needed to ensure that workers are safe in the face of the various risks associated with the water industry.

For more information: power plants: operation, advantages and disadvantages

Environment: gas risks in waste management

Diagram: waste management

Waste is any material, substance or product that has been discarded or abandoned because it no longer has a specific use.

Our society is a consumer society, but in recent years we have seen some changes. We are increasingly aware of the need to consume in a more responsible and sustainable way, giving priority to reuse, recycling and avoiding waste disposal in order to save resources.

Waste management is therefore another strategic area for preserving our environment. As with waste water, energy recovery is a preferred treatment method for waste disposal. The aim is to recover energy in the form of heat or electricity during waste treatment.

Energy recovery can be carried out directly, for example at waste collection centres, where the waste is burnt. Or indirectly, through the production of a solid recovered fuel or gas in gasification or pyrolysis processes: this is methanisation.


However, anaerobic digestion processes using this waste generate specific risks:

  •     Chemical risks from fermentation products such as ammonia, hydrogen sulphide and carbon dioxide
  •     Risks of asphyxiation, since the formation, transport and burning of biogas generates oxygen-poor atmospheres
  •     Risk of explosion, as methane is highly flammable
  •     Biological risks due to the micro-organisms contained in the digestate
  •     Risks of falling from pits

The TVL-TWAs for the main hazardous gases in biogas are shown opposite:


The operation of anaerobic digestion plants in the waste treatment sector requires appropriate preventive measures, particularly in terms of gas detection.

When working on the facilities, operators must have a portable detector that permanently indicates the various concentration levels and is small enough not to be in the way. The portable detector is not personal protective equipment (PPE), but a danger warning device. For this reason, two alarm thresholds must be defined:

  •     Threshold 1: alarm triggered to stop work in progress and analyse the situation
  •     Threshold 2: the alarm is triggered to evacuate the premises.

Similarly, installations are monitored by fixed gas detection systems. This equipment must be positioned correctly to sound the alarm. They are generally :

  1.     As close as possible to the source of emission
  2.     In confined spaces
  3.     Outside draughty areas (more than 1.5m0m from a door)
  4.     Away from air vents and near escape vents

As with portable gas detectors, there are two alarm thresholds. The recommended alarm thresholds for gas detectors are shown opposite:

Periodic checks and equipment maintenance


Periodic checks on work equipment and personal protective equipment are governed by regulations. Employers must ensure the safety of their staff and check that any equipment provided is fit for purpose. Any equipment that has deteriorated or is likely to create a hazard must be brought up to standard for its intended use, or if this is not possible, it must be scrapped.

  •     Portable detectors must be checked regularly (ideally before use) using a verification station. This allows the device to be placed in the presence of a gas of known concentration and the response time and trigger thresholds to be checked.
  •     The fixed detection system must be commissioned and maintained in accordance with the manufacturer's instructions. The detectors must be checked regularly with each of the reference gases.
  •     PPE for respiratory and fall protection is regulated and required by the Labour Code: a check before each use and an annual check by a specialist.

Checks on fixed or portable detection equipment and PPE must be carried out by a specialist to ensure optimum use and effectiveness.

Don't hesitate to contact our maintenance centre or our website