«PERSONAL PROTECTIVE EQUIPMENT PERSONAL PROTECTIVE EQUIPMENT PRACTICAL RADIATION TECHNICAL MANUAL PERSONAL PROTECTIVE EQUIPMENT INTERNATIONAL ATOMIC ...»
If, in addition to RPE, protective clothing is to be used, then the total ensemble has to provide the necessary protection factor. The specified protection factor might not be achieved in practice for various reasons. For example, if equipment that relies on a face seal does not fit the size and shape of a worker’s face, the necessary seal will not be possible. Facial hair, even growth over the working day, will lift some masks, possibly by enough to allow inward leakage of contaminated air. In these circumstances, or perhaps to permit prescription spectacles to be worn, RPE such as hoods, visors, blouses or suits would be a better alternative. The problem of facial hair also may be addressed by means of administrative requirements for all potential male users of RPE to be clean shaven.
Although APF and NPF are used interchangeably in this document, there can be significant differences depending on national regulations and standards. In using the system described (in Section 17), for example, a regulatory authority may specify and enforce the use of RPE with an NPF of 3 for work in situations of low hazards, but may require the use of RPE with a higher factor of at least 100 for continuous use as a standard general purpose respirator for work with radioactive substances.
Selection of suitable respiratory protective equipment.
An adequate APF/NPF has to be combined with meeting other conditions. The APF/NPF is the best theoretical protection that the RPE can provide, but this might probably not be achieved in practice. RPE must be used properly to give the best protection.
Filtering face piece (FFP) respirators are made wholly or substantially of filter material (P) which covers the nose and mouth. The face piece is held in place by straps and a nose clip (N), which helps to complete the seal. Air is drawn through the material by underpressure when the wearer inhales. Some models incorporate an exhalation valve (V). FFP respirators are mainly used for protection against low to moderately hazardous particles. They should not be confused with nuisance dust masks which only filter larger, low hazard dust particles. Some models are capable of filtering malodorous (but not toxic) gases and vapours.
The nominal protection factor of FFP respirators is relatively low, but the highest retention efficiency filters, class FFP3, provide adequate protection for either low risk and limited risk areas or for short exposures within the specified limits. Their use helps to keep contaminated gloves away from the mouth area but they provide no protection for the eyes and should not be used where skin contamination is a hazard. FFP respirators are easy to use and relatively inexpensive. They are usually described as disposable, for a single shift or single use only, and they should not be reused. They may retain contamination that can be monitored as an aid to assessing working conditions.
The elastomer half mask or orinasal respirator is a face piece (P) of rubber or plastic moulded to cover the nose and mouth and is held in place by adjustable straps. Air is drawn through one or more filters (F) and, where fitted, an inhalation valve (I). The filters are contained in one or more cartridges (canisters). Exhaled air is discharged to atmosphere through an exhalation valve (V) in the face piece.
Replaceable filters are available for particulate contaminants, gases and vapours. Their NPFs are usually much higher than for disposable FFP respirators but their real advantage is that the filter cartridges have a higher absorption capacity for gases and vapours and provide safe containment for subsequent disposal of the contaminant.
Specified gases and vapours are usually absorbed in a bed of activated carbon (charcoal) which may be impregnated with suitable chemicals to enhance the capacity to absorb or react with certain classes of chemicals such as acidic gases. If the contaminant is in the form of an aerosol, both particles and gases and/or vapours may be present in the workplace air and a combination of particulate and activated charcoal filters has to be used.
Half mask respirators provide no protection for the eyes and should not be used where skin contamination is a hazard.
Half mask respirators with single and multiple cartridges.
Different cartridges are designed to filter particulate materials, vapours and gases from the air before it is inhaled. Contaminants are safely contained within the filter cartridge.
A moulded face mask of rubber or plastic covers the entire face from just below the hairline to beneath the chin and is held in place with an adjustable head harness. Air is drawn through one or more filters and, where fitted, inhalation valves. Exhaled air is discharged through an exhalation valve (E) in the mask. Various models are manufactured, with either a single panoramic visor or individual eyepieces. The inner nose cup mask minimizes the possibility of misting (‘fogging’) and prevents the buildup of carbon dioxide. To prevent fogging due to moisture in exhaled air, antifogging compounds should be applied to the inside of the visor or the full face mask. The face mask can incorporate a speech diaphragm or microphone and provision for prescription corrective lenses.
The range of available filters is described in Section 20. The larger or multiple cartridges (canisters) can be used, with more comfort than is provided by the half mask, to extend the duration of use. The low inward leakage at the face seal enables the use of high efficiency particulate air (HEPA) filters, which would be over specified for filtering half masks.
Particulate filters indicate the end of their useful lifetime by the increase in resistance to breathing. A noticeable loss of resistance may indicate a hole or leak in the filter, face seal or cartridge (canister) gasket. Carbon (charcoal) filters cannot be tested and there is no feasible method to establish the residual capacity of a filter when it has once been used. The NPF offered against particles by a properly fitted full face mask respirator could be high.
The wearer has to monitor the apparent protection being provided by RPE and has to leave the designated area if there is any noticeable deterioration.
Full face mask respirators with visor or individual eyepieces.
Usually a seal has to be removed before a cartridge is used for the first time. Larger and/or multiple cartridge masks extend the period over which the respirator may be used. Full face masks provide protection for the eyes against radioactive contamination.
Powered air purifying respirators provide a continuous flow of air into the mask in order to minimize inward leakage of contaminated air around an incomplete face seal. Ideally, the NPFs are then only determined by the filter characteristics and are higher than the NPFs of non-powered respirators.
Contaminated air is drawn through one or more filters by a battery powered fan and the filtered air is delivered to the mask. The ventilator is usually mounted on a belt but it may be incorporated into the mask. Half masks or full masks may be used but the latter are preferred. Exhaled air is discharged to atmosphere through valves of various designs in the mask. Filters are available for particulate contaminants, gases and vapours. These respirators use approximately three times as many filters as their non-powered counterparts because of the increased airflow.
Powered air purifying respirators are desirable under conditions of increased workload because they make breathing easier. If the ventilator fails, the face mask gives the wearer enough time to escape a contaminated area.
Filtered air is pumped into the mask. Positive pressure inside the mask improves the NPF and makes breathing easier for demanding work. The filters are likely to need to be replaced more frequently because of the increased air flow through them.
Powered ventilated visors and helmets normally comprise a head covering, which may be a soft hood or a helmet to provide physical protection. A clear visor covers the face and an elasticated ‘skirt’ may enclose the area between the bottom of the visor and the neck or face.
Contaminated air is drawn through one or more filters by a battery powered fan and the filtered air is directed downwards over the face. The ventilator, incorporating the fan and filter(s), may be mounted on a belt or fitted inside the helmet between the head harness and the helmet shell. The equipment is less dependent on a face seal to achieve the NPF and provides a high degree of comfort for the wearer. In some situations metal helmets may be more suitable because they provide better protection against beta irradiation resulting from surface contamination.
The protection factors depend significantly on the type and circumstances of the task. Such equipment is normally used for protection against dust and other particulates but some models are available for protection against gases and vapours. Ventilated visors can offer high NPFs but some helmets offer quite low protection. If the ventilator fails there is a possibility of exposure as a result of the drastically reduced protection. They are therefore best for use in low hazard situations or where prompt egress from a contaminated area is possible.
Ventilated visors and helmets provide greater comfort than masks. Visors have high APF/NPF values but those for helmets are likely to be much lower. Helmets can protect against physical hazards and external exposure. Failure of the ventilator may cause a serious hazard.
Powered hoods completely cover the head and are made partially or totally of transparent material that offers minimum distortion or interruption of the wearer’s vision. Blouses cover the upper half of the body and seal at the wrists and waist. Suits cover the whole body and may incorporate boots and/or gloves.
Contaminated air is drawn through one or more filters by a battery powered fan and the filtered air is fed directly into the hood, blouse or suit and is exhausted usually by leakage from the protective clothing or through exhaust valves. The ventilator is usually mounted on a belt. Filters, as described in Section 20, are available for dusts, gases and vapours. The shelf life of the filter canisters is limited but, provided that the seal is not broken, they can remain effective for years.
Workers will need more extensive practical training to use hoods, blouses and suits than is necessary for the RPE previously described. They should be prepared for being dependent on the equipment to provide an air supply. They may need assistance to don and remove the RPE. The inner surfaces of the equipment must be disinfected hygienically and the outer surfaces monitored and, if necessary, decontaminated before reuse.
25. FRESH AIR HOSE BREATHING EQUIPMENTFresh air hose breathing equipment comprises either a half or full face mask.
The inlet of the hose contains a strainer and is secured by a spike or other means outside the contaminated atmosphere. Air is supplied by either normal breathing (unassisted ventilation), manually operated bellows (forced ventilation) or a powered fan unit (powered ventilation). A large diameter air hose is necessary which, for unassisted ventilation, should not be longer than about 9 metres. Such equipment is vulnerable, heavy and more cumbersome to use than compressed air line equipment (see Section 26). It is not suitable for use in nuclear facilities.
Large diameter hose must not be too long. The hose is cumbersome and vulnerable.
Air intake is fixed in a non-contaminated area. A strainer but no filter is used to minimize resistance to air intake.
A compressed air line may be used to supply a face mask, a hood or a blouse.