A breath of fresh air

The oil and gas industry is one of the most safety critical industries in the world. By the very nature of the material being explored for or extracted, it is inherently hazardous. The sometimes remote locations of the natural deposits of Oil & Gas, offshore or onshore, means that companies operating in this industry often find themselves in some of the most, diverse and extreme geographical regions around the planet. They are faced with extremes of weather and temperature, all of which make operating conditions difficult. Combined with the remoteness of their operations, these companies need to plan meticulously for any eventuality and be relatively self-sufficient.

One of the many areas of responsibility where oil and gas companies have to protect their workers, is personal protective equipment and, more specifically, respiratory protection. A small leak of H2S can damage health, large leaks can be fatal, and low oxygen levels in confined spaces can quickly lead to unconsciousness and death. Selecting the right respiratory protection equipment is therefore vital.

In building up a proper respiratory protection program, there are various areas to be considered. These include the early warning of the hazard, monitoring of the hazard and quick response to the hazard. Considerations must be given to whether it is necessary to continue working within the hazard, and whether or not you must escape from that hazard. It is arguable that respiratory protective equipment should be a last resort, because your risk assessment should ideally have removed the risk in the first place. In industries such as this one, however, this is not always possible.

Different gases require different respiratory solutions, so the type of equipment specified is very important. Respiratory protection equipment (RPE) stretches from ‘comfort’ protection, to working in increased levels of toxic gas, to immediately dangerous to life and health (IDLH) applications. There are many types of RPE utilised in the oil and gas industry today.

At this point, an explanation of the types of RPE available might be useful in assisting specifiers to choose the right application. RPE comprises two main types: ‘air supplied’ and ‘air purifying’, both of which can be ‘self contained’ and ‘non-self contained’, as shown in diagram 1.

Air-supplied RPE supplies the user with air from a source independent of the ambient atmosphere. Below is a brief description of the types detailed in the diagrams.

Self-contained RPE are made up of either ‘open-circuit’ or ‘closed-circuit’ types. An open circuit apparatus releases all exhaled air into the atmosphere through an exhale valve in the face piece and provides the user with clean air to breathe via a filter, cylinder or external air source. The closed-circuit system does not release the exhaled air, but recirculates it through the apparatus and removes CO2 from the exhaled air. Oxygen is then added back into the circuit so that the recycled air can be breathed again.

Open-circuit RPE utilises either ‘filtered’ or ‘Compressed Air Breathing Apparatus’ (CABA) types or ‘Fresh Air Breathing Apparatus’ (FABA) varieties. CABA is most commonly used for fire fighting applications.

Non-self contained RPE consists of an external air source, i.e. fresh air hose, or compressed air being supplied from a cylinder(s), airline trolley or a compressor. These are ideal for confined space entry, extended duration use and generally where conventional CABA are not appropriate due to either size, duration or condition restrictions.

Air purifying respirators
As the name suggests, air purifying is a method whereby ambient air is taken and purified so that it can be breathed. It relies on a filtering mechanism, which are used in personal protection equipment (PPE), defined as negative pressure and powered air purifying respirators (PAPR).

Filter technology is becoming more advanced, but does have limitations, most notably that filters should not be used in atmospheres that are suspected to be IDLH, oxygen deficient, where the ambient or contaminant conditions are unknown, or in confined spaces, such as, sewers and tanks. There are, however, many benefits, such as application specific head-top designs that are lightweight, durable, lower cost, compact or require less maintenance. Therefore, it is worth explaining the types of filter classes and types available.

Particle filters are approved to P1, P2 or P3 categories, being a measure of the efficiency of the filter media. These filter classifications account for the level of efficiency associated with the filter media. P1 (solid particles of inert substances) relates to 80 percent efficiency, while P2 (solid and liquid particles of low toxic substances) relates to 94 percent efficiency.

A P3 classification, or Class 3 for PAPR units, relates to 99.95 percent filtration success of solid and liquid particles of a toxic and highly toxic substances, for example: asbestos, radioactive and toxic particles, as well as microorganisms such as bacteria, viruses and enzymes.

Gas filters are manufactured from activated carbon. The efficiency of a gas filter is dependant on the filtering surface, carbon volume, granule size and pores in the carbon, the physical adsorption and the chemical absorption. Specific filters are designed for particular gases, for example, organic, inorganic, acids and ammonia.

The gas life of a filter is often difficult to determine as factors such as humidity, temperature, breathing rate and gas concentration will all have an influence. Caution should be used in trying to calculate filter life, as very often halving the concentration will less than double the gas life. The filter should be replaced before the filter life is exhausted to prevent any contaminant exposure to the wearer.

Combination filters combine particle and gas filter elements.

Powered air purifying respirators
PAPR units essentially pull air through the filter media and deliver the purified air into the user’s mask or headtop, typically at 120-200 litres per minute. Due to the benefits of positive flow rates and lower breathing resistance, the availability of task-designed headtops that are compatible with special apparel, the future will see more PAPR units used in certain scenarios, such as containment of spills.

Compressed air breathing apparatus (CABA)
When first used in the 1920s, CABA duration was approximately 20 minutes, but since this time, major advances have taken place. Cylinder technology has developed from heavy steel to alloy steel, aluminium, glass-hoop wrapped aluminium and glass full-wrapped cylinders, to the current technology of fully wrapped carbon fibre cylinders with steel, alloy or plastic liners. In most cases, the maximum filling pressure is either 200 or 300 bar. As well as cylinder advances, CABA have moved from negative pressure to positive pressure via a manual switching mechanism, to the current first breath activated positive pressure systems.

Harnesses have also changed to be much more flame resistant, currently being manufactured from Kevlar material.

Mask design has also improved with the utilisation of superior materials, enhanced visor profiles to increase vision, greatly improved speech diaphragms, and voice amplifiers and communications devices that can be integrated onto and into the mask. When speech enhancements such as amplifiers or communication devices are utilised consideration should be given to flame retardancy and intrinsic safety. Many of the devices currently available offer apparent speech enhancement without any consideration to the flame testing requirements of the mask and the environment it is used in, hence, loss of communication can occur in severe environments.

Airline breathing apparatus

Airline sets can come as constant flow sets and positive pressure sets and are suitable for a wide range of applications. Constant flow sets have lower protection factors than positive pressure and are therefore used in non-IDLH atmospheres where there are low levels of contaminants. The benefits of these types of sets is that they have a variety of headtops and are therefore ideal for a range of different applications, as well as being very comfortable. Positive pressure sets use a tight-fitting facemask and offer an assigned protection factor (APF) of 2000. They are ideally suited to working in areas of high levels of toxic gases or low levels of oxygen. For increased safety, optional escape cylinders can be added to the set, which can be used should the airline supply fail. These sets can be fed from portable trolleys or trailers or more likely via a cascade system.

Escape breathing apparatus

Escape sets can be of two types, constant flow and positive pressure. A constant flow set will provide the user with a fixed flow of air for a fixed amount of time from when the cylinder valve is opened, the disadvantages of this are that if the wearer can theoretically out breath the air supplied from the set, the advantage is that the set will last the duration that it states. For more arduous escape routes and for increased protection factors in areas where there is likely to be a high level of toxic gases present then positive pressure escape sets are available. These will provide the wearer with as much or as little air as the wearer requires and will therefore either last longer or shorter than the stated duration. This allows a positive pressure escape set to provide an APF of 2000. Modern versions of escape sets now automatically activate upon opening the bags and some are even supplied with ancillary air in connections allowing them to be connected up to cascade systems at muster points should an increase in duration be required.

Air quality
Technology has advanced considerably over the last few years for RPE, however, little attention has often been given when refilling or recharging breathing apparatus cylinders. At present, many users test the air quality of their compressors after a certain time period or number of hours that the compressor has been used. Little has been done process or product wise to prevent a technician inadvertently filling a cylinder with potentially contaminated air. An air quality check that may have been performed earlier that day, may be of a satisfactory standard, however, the compressor could be compromised later by many factors, including, the compressor operator who may have unwittingly placed the intake in the vicinity of fumes or exhaust. The compressor needs to have a device which constantly monitors the air quality, and that immediately shuts it down before any contaminated air enters the cylinder.

Cylinder failure rarely occurs during recharging, however, instances have occurred with catastrophic consequences. Many compressors are located outside a facility and the recharging of cylinders undertaken inside sometimes with the cylinder in a bath of water or behind a barrier, which is usually un-engineered. Current best practice is the utilisation of a containment facility that provides assured protection for personnel and plant. The Scott Revolveair is an example of what can be fitted to any brand of compressor.

Conclusion

Ultimately oil and gas workers have never had a better opportunity than they do today to be protected against the external environment in terms of respiratory protection. Products are now available to suit every application, offering workers differing levels of comfort and protection and the ability to continue working in the long and short duration. Operators in the oil and gas segment can now employ cost effective and integrated servicing programmes. Often the advantage of using a single manufactured brand of respiratory protection is it allows the same types of spares to be utilised and permits straightforward servicing methods. A good example of this in practice is illustrated by the high number of interchangeable parts between negative pressure facemasks and CABA facemasks.