A “hazardous area” is defined as an area in which the atmosphere contains, or may contain in sufficient quantities, flammable or explosive gases, dusts or vapours. In such an atmosphere a fire or explosion is possible when three basic conditions are met. This is often referred to as the “hazardous area” or “combustion” triangle.
In order to protect installations from a potential explosion a method of analyzing and classifying a potentially hazardous area is required. The purpose of this is to ensure the correct selection and installation of equipment to ultimately prevent an explosion and to ensure safety of life. The methods used to classify an installation generally are of two main types of classification. In countries that have adopted the IEC (International Electrotechnical Commission) philosophy this is referred to as Zoning whilst in North American installations are classified by Classes, Divisions and Groups to ascertain the level of safety required.
HAZARDOUS AREA CLASSIFICATION: IEC AND ATEX( Atmospheric Explosible) STANDARDS
A Hazardous Area is defined by three main criteria, these being:
- The type of hazard (groups)
- The auto-ignition temperature of the hazardous material (temperature or “T” rating)
- The likelihood of the hazard being present in flammable concentrations (zones)
Hazardous substance safety precautions
Once you have identified any risk of exposure to your workers, you then need to consider how to protect them. You should consider control measures, in the following order. These are known as a hierarchy of controls.
- Eliminate the use of a substance.
- Use a safer form of the substance, for example a readymade paste rather than a powder.
- Change the process to emit less of the substance, including waste streams.
- Enclose the process so that the substance does not escape.
- Extract emissions from the substance near the source through exhaust ventilation.
- Minimise the number of workers who could be exposed to the hazard even with controls in place.
- Provide personal protective equipment (PPE), for example gloves, coveralls and respirator (these must fit the wearer and provide the correct protection for the task, the substance and the work environment).
You should also ensure that
- you provide appropriate protective equipment free of charge
- workers are properly trained to use control measures correctly
- workers understand the process and the hazards associated with it
- you keep records of issue, and checks and maintenance in logbooks
- you follow the recommended schedules for checking, maintenance and testing of your systems.
Accidental exposure :
Even the best controls can fail at some point. It is important to plan and practice how to deal with accidents such as spills, and emergencies such as
- splashes on skin or eyes
- a leak from a gas or fume
- a worker losing consciousness.
You need to ensure that the control measures you put in place remain effective. This may mean that you need to carry out exposure monitoring involving taking air or biological samples. If a risk of exposure remains you may need to carry out health checks. These could include skin checks for dermatitis or health surveillance on exposed workers.
Local Exhaust Ventilation (LEV)
LEV is an engineering control system for reducing exposure to
- airborne dusts
- solvent vapours
- metal and rubber fumes.
Most systems will have the following.
- Hood, which captures contaminants in the air.
- Ducting, which transports the air and the contaminants mixed in it towards the air cleaner/arrester or to the discharge point.
- Air cleaner or arrester, which filters particles or microorganisms through a filter bank to clean the air. Not all systems have air cleaners or an arresters.
- Air mover, which transports the air and contaminants through the system.
- Discharge point, where contaminated or cleaned air is discharged safely.
If LEV is required, you should
- look at the relevant trade good practice guides for the processes where LEV is needed
- identify what the LEV needs to do, for example extract vapours, mists, fumes or dust particles
- seek advice from a reputable supplier or specialist to ensure the right design is constructed and installed
- regularly maintain and check that the equipment is doing its job correctly
- keep records of maintenance and inspection.
Make sure that the introduction of LEV does not create other safety or health risks such as loud noise or reduced access.
Respiratory protective equipment (RPE)
In the control of substances hazardous to health (COSHH) hierarchy of controls, use of RPE should not be the first or only precaution taken to protect your workforce. It is however a very good temporary precaution while you make arrangements for proper protection.
The equipment must :
- fit the wearer
- be the right type for the task, the substance and the work environment.
Long term use of RPE must only be considered when exposure cannot be adequately reduced by other means. It is important that you chose the right RPE for the job, it must reduce exposure as low as reasonably practicable (below any applicable workplace exposure limits or other control limits).
RPE must fit the face of the wearer properly to be effective. Face-fit testing must be carried out to ensure the chosen face piece adequately fits and protects the wearer. This includes testing of full-face masks, half-face masks and disposable masks.
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