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Baseefa Ltd

Gas Mapping – is it worth it?

06 September 2017

On premises where flammable or toxic gases are stored or used, suitable and sufficient gas detection is required. The goal of this article, by Randall Williams of Proeon Systems, is to outline the importance of a gas detection survey to demonstrate that the responsible persons within companies have done all that is reasonably practicable to protect any operatives from risk

Gas Detection Systems are required to protect people and assets wherever hazardous situations exist due to the presence of flammable or toxic gas. The author has been involved with Fire Safety since 1987 and with each passing year technological advances have provided better detection and safety systems. Specifically, gas detection systems are more sophisticated and the gas detectors have better response times and fault reporting. However no matter how good the gas detectors and system are if the detectors are not in the correct position then the system falls short.

Gas detection mapping or surveying is when a qualified and competent person designs the location of the gas detectors to reflect the risk of a potential toxic or flammable gas leak. The process can be supported by the use of 3D modelling software that illustrates the risk (grading), and detection coverage. This has many advantages over simple paper exercises.  Increasingly the Health & Safety Executive (HSE) is requiring sites to demonstrate the risk is covered and assessed by reviewing the Gas Detection Survey Report or Audit.

The legislation is clear. On the 1st February 2016 the HSE in the UK released new guidelines regarding sentencing for Health & Safety breaches responding to; ‘concern that previous fines for serious and fatal corporate health and safety offences were too low in relation to the harm caused.’  Included in the guidelines rated as ‘High’ culpability it states; ‘failing to put in place measures that are recognised standards in the industry.’ In the United Kingdom COMAH Sites (Control of Major Accident Hazards), the regulations are clear and audited by the HSE. 

However, a number of sites will have large quantities of flammable products, but fall below the legal requirements to be registered as a COMAH site.  The duty is clearly placed on the ‘Responsible Person’ to protect people from the risks related to dangerous substances and potentially explosive atmospheres.

The issue is that normally the ‘Responsible Person’ (the person who is in control of the building, premises and its use) will not have the training, skills or experience to design or review the Gas Detection Locations to the standards required by HSE. It is typical and sadly not unusual to find a number of dangers observed on ‘non COMAH’ sites. On observation of the author these have included:
• Gas Detectors disconnected because of faults
• Gas Detection panels altered to mask faults
• No Current DSEAR (Dangerous Substances and Explosive Atmospheres Regulations) Reports
• No existing or out of date Hazardous Area Mapping 
• Fire Risk Assessments that mention ‘Flammable Substances on site’ but do not detail DSEAR recommendations
• Gas Detection Panels installed in the area of risk
• Inadequate staff awareness of flammable atmospheres with the appropriate training.

Gas / Fire Detection Systems do not prevent releases of toxic or flammable gases, fires or explosions. They are one part of a series of ‘Layers of Protection’ in place to manage or mitigate the risk. As with any safety system there is a process to ensure that the Gas Detection System is always ready to detect accumulations of flammable or toxic gases.

Part of a Process - Hazardous Area Safety System Cycle

Most safety professionals are familiar with ‘cycles’ to facilitate continuous improvement. Proeon Systems have developed a system for Gas and Flame detection systems that provide guidance for each assessment or design. 

Without going into detail, each step of the process is essential and requires differing levels of documentation. Sub-contractors and suppliers can support during the process, however the ultimate responsibility lies with the Responsible Person at site or within the operating Company.  Specifically when designing a new system it must be clear who takes design liability for the gas detector locations. When gas detection suppliers are involved, it should be clear who is responsible for the gas detector locations. This documentation demonstrates that the system is being designed and managed.

When does a company need a Gas Detection Survey?

• New Systems: When a risk assessment determines a requirement for a Gas Detection System, the Gas Detection Survey will provide the confidence that the field detectors are located in the correct positions to provide the required coverage.
• System Upgrades: When systems are upgraded or significantly changed regulators recommend a review of the design to ensure the system is adequate.
• Changes in Process or Building: When any change occurs within a process or building, risk assessments should be updated.
• Periodic Reviews: Systems should be subject to periodic reviews. COMAH sites require five year reviews due to their hazardous nature. The Gas Detection System is often a safety related system and should be reviewed on a regular and documented basis.

For the Risk Assessment in simplistic terms within the context of flammable or toxic gases, the questions raised are, ‘What are you using?’ and ‘How are you using it?’  Every good risk assessment should identify who or what is at risk and why they are at risk. The Risk Assessment is the starting point for the Gas Detection Mapping. Additionally the site should provide some form of detection targets. The Oil and Gas Industry have years of practice to develop detection targets to standardise the design of their installations.  Many non-COMAH sites do not have their own standards, so prior to the survey a formal statement of requirements should be agreed. The statement should detail how the Gas Detection system is to perform, giving tangible targets based on risk assessment and quantification of hazards.

The Value of an Independent (Third Party) Gas Detection Survey / Audit

A mentor hijacked Socrates when he said to me, ‘We don’t know what we don’t know, but a smart man knows who to ask.’ It is unrealistic to expect most Responsible Persons or Companies to have the skill set and resources to objectively report the gas detection is suitable and sufficient as required by the HSE.  The correct independent Third Party advice will provide the required documentation to demonstrate the Responsible Person or Company has done everything reasonably and practicably possible as required.

A Third Party is also valuable to clearly identify the areas of risk. A ‘fresh pair of eyes’ will require the risk to be defined which will provide clarity when reporting to a regulatory body. This is also an opportunity to define existing and planned mitigation.  For example, a site with a risk of toxic gas might only be accessible by a long set of stairs, the mitigation can be:
• Seals on doors to prevent the spread of toxic gas.
• Pressurised stairwell to prevent gas entering when the door is open.

The Third Party can look at the risk from a global perspective to provide insight to the specific situation.

Additionally the Third Party can reflect deficiencies and failings in process and procedures. Recently; while undertaking a Toxic Gas Detection Survey, Proeon increased the number of gas detectors in a remote area application. The Plant Manager did not see the need for gas detection in this area, until he understood the distance of travel for operatives to evacuate to a place of relative safety, they required an earlier warning.

Many Oil & Gas companies have or had their own team of in-house experts. In all likelihood most sites do not have a person trained or experienced enough to assume this responsibility. The Independent Third Party provides the Responsible Person confidence that the gas detection system is designed correctly.

Hallmarks of a good survey

So what do you look for when choosing someone to carry out a Gas Detection Report?  Here are a few indicators to look for in a good report:
• The right person – You may have to make some assumptions regarding the competency of the groups or individuals to prepare the reports, however a fire safety professional will understand the multiple layers of systems and mitigation, whereas a site specific engineer or process engineer may not appreciate how one process can affect the wider fire safety issues.
• The right tools – There are a number of 3D Gas / Flame Modelling software packages available and they each have their own strengths and weakness. Normally the software is not the issue, it is the person using it that makes the difference (see point above)
• Understandable - A competent engineering company will provide a structured report with key elements to demonstrate the report is correct and verifiable demonstrating competency.
• Identifies risk and grades – Risks need to be identified and the appropriate grading for these risks. Flammable gas detection will usually have a ‘Hazardous Area Report’ identifying where gas can be present. Toxic Gas usually is not so straight forward and relies upon the site risk assessments.  Once the risk is identified each should be graded for risk.
• Provides recommended solutions – An audit will plot the coverage based on existing detection, with recommendations to modify the design if required. New systems should place detectors in practical locations that can be mounted and serviced.
• Demonstrates coverage adequate (percentages) – Referring to the detection targets or standard of design, how does the proposed system meet the detection targets?

Recommendations and action plan – In the same way a fire Risk Assessment has an Action Plan, the report should summarise the observations / recommendations with clear actions that should be completed or mitigated. Sample of Report Recommendations below: 


To quote a Health & Safety Consultant - Max Geyer, “The point is that being able to demonstrate ‘due diligence’ is not about having a thing (a policy or a system or a heap of procedures and checklists) it is about doing a thing”.

It is everyone’s interest to be safe AND productive.  The two are not mutually exclusive, however, safety is often seen as expensive and ‘over the top,’ by blasé managers.

Nevertheless, the moral and likely legal obligations require provision of a suitable warning system to the presence of unignited / dangerous substance. Independent Gas Modelling Survey and Report is a key element to demonstrate compliance. Without the report there is no adequate documentation for the courts in the event of a prosecution, or a reasonable excuse for those affected by an incident involving flammable / toxic gas.

1.  Health & Safety at Work Act 1974 (HSWA).
2.  The Control of Major Accident Hazards (COMAH) Regulations 2015 (L111, Third Edition).
3.  The Dangerous Substances and Explosive Atmosphere Regulations 2002 (DSEAR).

About the author

Randall Williams has been working in the fire safety industry since 1988 as a Fire Alarm Engineer and Fire Risk Assessor.  He is a Third Party Certified Fire Risk Assessor by the Institute of Fire Engineers and is a member of the Industrial Fire Risk Special Interest Group for the IFE. Randall leads the Fire & Gas Team at Proeon Systems in Norwich, UK. 

He is a Graduate of the Institute of Fire Engineers (GIFireE) in 2013 and graduated with BSc Fire Protection Management & Technology from California State University, Los Angeles, California in 1986.

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