Confined space gas detection

All you need to know

In this article we are going to be taking an insight into the world of workplace health and safety – including what a confined space is, what the risks in a confined space are and best safety practices to follow in this environment.

What is an enclosed space?

According to the Oxford compact English dictionary, an enclosed space is defined as: “shut in on all sides” and “secluded from the outside world”. ‘Enclosed’ suggests that a person who is entering / working / existing in such an environment will have some restrictions.

What makes an enclosed space a confined space?

It’s important to note that an ‘enclosed space’ isn’t necessarily a ‘confined space’ and therefore doesn’t always have to be a cramped place.

A confined space is any place, such as a tank, vat, chamber, pipe, flue, silo, pit, trench, well or other alike location in which risks have been identified because of the enclosed space nature.

Detecting gas

Let’s start with the basics: what are the risks to be identified and controlled? There are many health and safety risks that can arise in a confined space – with one of the main hazards being harmful gases. The main risk of harmful gases being present in an enclosed area is the loss of consciousness or asphyxiation to an employee who is at work – caused by gas in the form of fumes, vapour or the lack of consciousness from a lack of oxygen.

It’s an employer’s duty to protect their employees and ensure their safety and health – this includes employers taking the time to understand and be aware of the hazards associated with confined spaces. Carrying out an assessment of the risks to health and safety ensures that employees won’t be exposed to a risk, and if there is a risk: is it to be made sure that it is controlled at an acceptable level.

“regular assessments of the conditions within and around the confined space should take place, to identify what gases are or could be present"

Risks of gas within a confined space

Next question: what should be included in hazard identification and assessment? Regular assessments of the conditions within and around the confined space should take place, to identify what gases are or could be present. These could be obvious ones such as those produced from cutting or welding but could be less obvious such as cleaning with chemicals – this work doesn’t necessarily have to be carried out specifically in the confines area, it could be an associated area.You should never forget to also assess which gases are potentially not present (i.e. oxygen).The three main constituent gases in air are nitrogen, oxygen and carbon dioxide. Air is colourless, odourless and tasteless – it supports combustion and is essential for respiration. As air is a combination of gases, it is possible for separate gases to be isolated through specific processes.

Confined space hazards – what are the risks?

  • Injury/death caused by fire or explosion
  • Loss of consciousness a person at work caused by increased body temperature
  • Loss of consciousness or asphyxiation of an individual at work caused by harmful gas, vapour, fumes or lack of oxygen
  • Drowning of any person
  • The asphyxiation of an employee at work caused by free flowing solid

Detecting gas, vapour or fume in a confined space

To keep employees as safe as possible, all confined space must be tested prior to persons entering. There are a few ways in which this can be achieved; either by carrying out tubing or by using a probe and drawing out a sample to insert into a detection device. In addition to this, an alternative way to detect gas, vapour or fumes in an enclosed space is by placing a detection device into the space itself and allowing it to record the conditions. An appropriate gas surveying device will record peaks and troughs of gas readings obtained from the confined space: these should be available to those assessing the risks.

Gas detection devices

Detection instruments can be supplied in various combinations of sensors. These vary from one sensor devices for a specific gas to multi sensor devices for a variety of gases.

  1. Gas detection devices vary depending on the design role of the software attached to the instrument – this can be as unassuming as recording the readings and noting if maximum trigger levels are reached.
  2. Choosing the right device for a certain confined space depends on the environment itself – including the potential gas, vapour or fume likely to be present – including oxygen levels.
  3. Chemical detector tubes may be an appropriate device for some confined spaces – but, if available, portable electronic devices that continually record the atmosphere where the person is working should be first choice.

Who should carry out gas detection testing?

The gas detection test needs to be carried out by a trained and competent individual who knows and thoroughly understands the features of the gases, fumes and vapours being distinguished.The tester should also understand the relevant legal requirements and standards in association with carrying out gas detection.

Gas detection best practice

To keep the gas detection process as safe as possible, in addition to complying by associated legislations, it’s a good idea to follow best practice steps.

Points to consider

When taking gas readings, it’s important to consider the following points:

  • Using a portable gas monitor is the best form of gas monitoring – this is because some gases can be lighter or heavier than air, meaning you’ll need to position the gas monitor into relevant areas
  • When taking gas readings, leave the device in a stationary position for a few seconds, as gas needs to be drawn into the monitor before it can be correctly analysed
  • If an alarm goes off, all workers should immediately leave the area – if not exited in time, people can be exposed to a toxic, explosive or an overall harmful environment
  • It’s important to note that the person who is taking the gas reading should not put their head above the gas monitor: this is due to the risk of a gas pocket being present, which can cause a lot of harm – including unconsciousness
  • Ensure there are no contamination from Diesel engines such as vehicles and generators to set a base level for carbon monoxide (hopefully very low). Then sample again with diesel engines running to ensure that the maximum level of carbon monoxide is detected. Ensure this maximum level detected is as expected and is a safe and legal level. Any increase from this level however small should be investigated and a reason for the increase found. If in doubt get the workers out until it is clear where the increase in carbon monoxide is from

Gas detection process roundup:

  • Identify your confined space
  • Discover the hazards
  • Pinpoint the risks
  • Manage the risks
  • Should the confined space need to be monitored – ensure that you have the correct gas device for the environment
  • Use/supply respiratory protection when required
  • Make sure that rescue arrangements are suitable and effective
“in addition to complying by associated legislations, it’s a good idea to follow best practice steps”

Remember it is your confined space and therefore, your problem – you have a legal duty to provide the safest solution.