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Safety in the Wind

Published: 01st Jun 2012 in OSA Magazine

gas detection Gas detection is the simple phrase used for ‘atmospheric testing’ or ‘atmospheric sampling’. The process involves capturing a sample of the atmosphere so it can be analysed to determine the percentage or amount of a particular substance in the atmosphere (the air we breathe).

Electronic gas detectors are most commonly used because of their ease of use, accuracy and instant results. An electronic gas detector can be equipped with one sensor or several, each for a different gas. The most common gases ‘detected’ for in construction, oil and gas and refining are: oxygen, hydrocarbons, carbon monoxide, hydrogen sulphide and benzene.

When do I perform gas detection?

• Confined space entry
• An area known for or suspected of having a toxic atmosphere or hazardous airborne contaminants
• An area known for or suspected of having a flammable atmosphere

Confined spaces

Gas detection is absolutely necessary for confined space entry – you must not risk sending a person into a confined space without knowing the contents of the atmosphere.

Your typical confined spaces include: barges, crawl spaces, holding tanks, hoarding, hoppers, manholes, pipelines, pits, pontoons, process towers, silos, sumps, trenches, tunnels, underground chambers, utility vaults and vessels.

For every confined space entry there must be a designated confined space attendant who is responsible for the gas detection of the confined space. Through the years I have witnessed and been involved with hundreds of confined space entry related work. I have seen very strong and very weak safety practises relating to gas detection.

Let me share what I mostly come across both in strong and weak practises.

Weak practise

• The gas detector has not been given the correct alarm values (refer to your local health and safety regulations)
• The gas detector has not been calibrated, or the last calibration has expired
• The gas testing person was not trained for performing gas detection
• The gas testing person did not function test the gas detector before performing the gas testing
• The gas testing person holds the gas detector an arm’ s length inside the manway for a few seconds to test the atmosphere
• The gas testing person does not record the testing results

Strong practise

• A gas detection programme is established and workers are trained
• The correct type of gas detector is selected for the testing required
• The gas detector is correctly programmed, calibrated and function tested
• The gas testing person has tested the confined space by using a probe attached to the gas detector or, if that was not sufficient, the confined space is tested by planning and executing a safe entry for the purpose of testing the atmosphere
• The gas testing person performs testing at a planned frequency and records the results

One man team

One thing that really, really, really bothers me with confined space work is the lack of rescue planning, and the lack of a properly trained and equipped rescue team.

I was working at a refinery that had a very strict enforcement for their safety rules. Because of this strictness I expected they would have very thorough rescue plans. Well, this was not so; this is what I encountered at one of their confined space projects for a large storage tank.

I noticed the rescue plan indicated only one person would be the ‘rescue team’. The plan was for this one man rescue team to enter the tank wearing supplied breathing air; however, the supplied breathing air was a SCBA with 100 feet of airline connected to it.

I asked what was the purpose of the airline? The reply was that the SCBA would stay outside of the confined space, the one man rescue team would don the face piece and would have 100 feet of airline connected to him. I was amazed!

I informed the person that the SCBA is worn like a backpack, that the airline is not necessary and it only supplies about 30 minutes of air, depending on how hard the person breathes. The airline would be a tripping hazard but, more importantly, the air would have to travel 100 feet before arriving to his face piece.
I explained that he would also be losing precious air because of this airline. Once the air cylinder is empty and the air is occupied within the airline, the air pressure will reduce with every breath – the pressure will reduce low enough that there will be remaining air in the airline that will be unable to travel to the face piece.

A couple of minutes of air might be the difference between a successful rescue or a body retrieval.

Thankfully this particular storage tank had very good ventilation in place and it was highly unlikely that the atmosphere would turn hazardous.

Gas detection practises

• Establish a gas detection programme which includes training and mentoring
• Assign a competent person
• Select the correct instrument for the hazards you are testing for
• Read and follow the instruction manual, keep the manual with the instrument’s case
• Use the correct calibration gas and equipment for the instrument
• Complete an entry plan if the testing person has to enter a confined space to perform testing – wear supplied breathing air
• Use a probe wherever possible – a probe attaches to an electronic gas detector with a length of hose long enough to reach the required areas; the probe draws air through the hose and to the gas detector’s sensors
• Determine a frequency for testing and record the results
• Protect the instrument from damage
• Prevent overloading a gas detector’s sensors; for example, do not place a gas detector by the exhaust of a running vehicle.

Coffee break

During a night shift three workers were completing welding repairs inside a storage tank. This storage tank was approximately 50 feet in diameter by 30 feet high and there was only one manway.

A confined space attendant was designated to remain posted outside of the manway while the workers worked inside. The attendant’s duties were to maintain communication with the workers, record their entry and exit of the tank and perform gas detection of the tank’s atmosphere.

The attendant was known for not liking these duties, just like many other workers; however, this particular attendant over complained, would show up late to the tank, and was hoping to be transferred from these duties if he did a lousy enough job.

It just so happens that three blocks away from the worksite was a coffee shop. At one point during a shift while the workers were inside the tank, the attendant decided to leave the post so he could go to the nearby coffee shop, buy coffee and donuts and bring them back for the workers before they came out for coffee break.

When the workers came out of the confined space for their coffee break they were shocked to see the attendant waiting for them with the coffee and donuts. If you have been involved with confined space work, you probably just shuddered at the thought of this story. I wondered how many times does something like this occur? Maybe not a trip to the coffee shop, but how about a trip to the tool crib, or office, or anywhere else that takes several minutes to walk to.

Practise wearing supplied breathing air

If you are responsible for performing gas detection, most likely you will need to wear supplied breathing air to protect yourself while performing the gas detection. Before actually performing this task for the first time I recommend you practise wearing supplied breathing air equipment. Any practise sessions should obviously happen in a safe, well ventilated environment.

• Practice donning and doffing the equipment
• Walk up and down a flight of stairs a few times so you have an idea of how much air you consume
• Practise cutting yourself off from the air by disconnecting the air cylinder and reconnecting
• Try this in the dark, resist taking off your mask – it is a freaky experience!

Flammable atmosphere

Gas detection must be continuous in a potentially flammable atmosphere. As a gas testing person or ‘fire watch’ you will be monitoring for an increase in oxygen levels and an increase in the combustible gases (hydrocarbons).

Practises for working in a potentially flammable atmosphere:
• Establish a hot work programme which includes training and mentoring
• Designate a ‘fire watch’ to continuously monitor the atmosphere
• Use a gas detector equipped with sensors for oxygen, hydrocarbons and other known flammable gases if necessary
• Ground and bond equipment and machinery – eliminate static electricity
• Use non-sparking tools
• Have fire extinguishers readily available
• Wear flame resistant garments
• Use spark shields/welding shields to contain sparks from welding, gouging, grinding and torching
• Use fire blankets to protect equipment, material and machinery from sparks and open flame

Toxic atmosphere

Gas detection must be continuous in a toxic atmosphere. As a gas tester you will be monitoring for a decrease in oxygen levels and an increase in the toxic gases such as hydrogen sulphide, carbon monoxide or benzene.

Practises for working in a toxic atmosphere:
• Establish a respiratory protection programme which includes training and mentoring
• Designate a gas tester to continuously monitor the atmosphere
• Install a ventilation system to remove the toxic gases and introduce respirable air
• Wear respiratory protective equipment


The ATEX directive consists of two EU directives describing what equipment and work environment is allowed in an environment with an explosive atmosphere.

These are broken down into directive 94/9/EC, pertaining to equipment and protective systems intended for use in potentially explosive atmospheres and the ATEX workplace directive, 99/92/EC, outlining minimum requirements for improving the safety and health protection of workers potentially at risk from explosive atmospheres.

Manufacturers looking to access and sell products for use in explosive atmospheres in Europe must demonstrate compliance to the ATEX Directive 94/9/EC.
Manufacturers of products intended for use in potentially explosive atmospheres must provide assurance that their equipment will not cause an explosion during routine operation. Demonstrating compliance with the ATEX Directive 94/9/EC provides that assurance. It is also mandatory for these products to bear both the Distinctive Community Mark (the Ex Mark in hexagon) and CE marking before being sold in the EU.

While ATEX certificates are mandatory in the EU, ATEX is also a frequent contract specification for countries outside of Europe.
There are a few important novelties in the Directive 94/9/EC for both manufacturers and users of equipment and protective systems intended for use in potentially explosive atmospheres:

• The Directive also applies to safety or control devices installed outside the hazardous area but having an explosion protection function (for example, Control Units installed in a safe area and connected to remote EX gas detectors installed in a potentially explosive area)
• All risks of explosion are considered (e.g. mechanical shock, overheating, acoustic and optical emissions, EM emissions) affecting both electrical and non-electrical equipment for use in potentially explosive atmospheres
• The Directive follows the guidelines “new approach” of the European Council, addressing general requirements e.g. “essential health and safety requirements” relating to the design and construction of equipment for use in potentially explosive atmospheres (Annex II)
• Based on the new approach concept, these essential safety requirements (ESR) address the basic criteria to assess the conformity of the equipment, even if there is a lack of specific harmonised norms, helping progress in the design and use of innovative products
• The Directive includes equipment for installation in both surface (Group II) and mines (Group I) environments, considering that explosion risk, protection means and testing methods are very common to both typologies, though the classification remains different
• Criteria are set to classify the devices by categories in function of the protection level and the zone of use. Different procedures on how to assess conformity are set in function of product and its category. For example, electrical devices of category 1 and 2 are subjected to certification of the prototype by a Notified Body (EC-Type Certification- Annex III) as well as to production surveillance by the Notified Body
• The equipment and protection devices conformable to the Directive are to be marked by the symbol of explosion protection (epsilon-X in a hexagon) as well as display a CE mark proving their conformity to the previously applicable Directives. Safety devices with a measuring function (like gas detectors) must meet a recognised performance standard, e.g. EN 50054, 50057 (EN 61779-IEC 1779) and EN 50271 for flammable gas detectors, within the scope of the ESR (Annex II 1.5.5 - 1.5.6)

Safety devices must function independently of any measurement or control devices required for operation (ESR Annex II 1.5.1)

Useful links

In the potentially volatile world of gas detection, it’s always worth consulting authorities to stay up to date with advice and legislation pertaining to it. Some are listed below:

American National Standards Institute
ANSI/ISEA 102-1990 (R2009)

ANSI/ISA - RP12.13.02-2003 (IEC 61779-6 MOD)

ANSI/ISA TR12.1303-2009

Canada Standards Association
CSA C22.2 NO.152-M1984 (R2011)

National Fire Protection Association
NFPA 72 - Chapter 17.10

National Institute for Occupational Safety and Health
NIOSH - Simulated Gas Detector Training

British Standards European Norms
BS EN 50402:2005+A1:2008


Whichever industry you are working in where gas detection is necessary, it’s clear that from potential explosions through to possible asphyxiation, gas is a hazard which commands meticulous and precise monitoring.

This is one of many areas in EHS where planning – in the shape of a thorough risk assessment, ensuing safety programmes and detailed record keeping – is essential to establish and maintain worker safety.

Published: 01st Jun 2012 in OSA Magazine


Paul Dreger

Paul Dreger is the creator of ooshew, an online resource dedicated to sharing information based on occupational safety, health, environment and wellness. The vision of ooshew is for all workplaces in all corners of the world to have equal and free access to the latest resources, to keep people and our environment healthy and safe from the hazards created in the workplace. Join ooshew today and start sharing your knowledge, experience and passion!

Paul Dreger




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