SOME SPECIAL CONSIDERATIONS FOR RESPIRATORY PROTECTION
DEVICE SELECTION
Some applications, by their nature, require special consideration to be given to Respiratory Selection. Some examples are discussed below.
Safe exposure standards have not been established for bacteria and virus and this gives rise to difficulty in deciding what level of protection is required. In general, high efficiency particle filters are required and these should be of a type approved for liquid aerosols.
Further than this, to decide what class of respirator is appropriate, it is necessary to consider at least the following:
(1) Proximity to contamination source
(2) Level of ventilation/ dilution
(3) Risk of contamination (e.g. by splash, from coughing etc)
(4) Infectious dose of the organism, for example TB is very infectious, whereas HIV virus is much more difficult to transfer
If risk from all of these factors is ranked low, it is likely that an FFP3SL disposable of half mask with P3 filter would be adequate. For progressively higher risks, higher levels of RPE would be required. If the level of risk cannot be identified at least qualitatively, it would be unwise to consider using anything less than TH3 or TM3 powered respirators against bacteria and virus.
Products that are used against bacteria/virus must be effectively decontaminated after each use and filters etc must be disposed of as controlled waste after each use. Measures to control exposure at source should always be used in addition to RPE.
B. ASBESTOS AND ASBESTOS REMOVAL
Deaths from asbestos related diseases are rising rapidly in most countries and it is probably the single largest respiratory killer after tobacco smoke. Asbestos exposure potentially affects many tradespeople in construction and maintenance industries e.g. plumbers, plasterers, joiners and electricians, as the use of asbestos in construction materials is not usually obvious to the untrained eye. Use of RPE fitter with effective particle filters is essential when working with asbestos containing materials, and even this will not be adequate unless suitable measures are taken to ensure dust levels are minimised, e.g. damping down, isolation of the work area, and avoiding drilling, sawing and breaking asbestos based materials where possible. In the UK, only licensed contractors, who are properly trained and equipped for this specialised work, can carry out significant tasks with asbestos.
Where work(e.g. removal, demolition, construction) which is likely to give rise to asbestos dust is contemplated, minimum TM3 power assisted respirator or EN139 positive pressure demand breathing apparatus should be worn. Full measures for controlling dust at source according to national legislation should be used in combination with appropriate work enclosures and decontamination procedures.
The RPE maximum use concentrations advised for RPE are as follows (for all typed of asbestos):
Suitable TM3 power assisted full facemask - 8 fibres/ml.
Suitable positive pressure demand full facemask Breathing Apparatus - 40 fibres/ml.*
*Note: No data showing the workplace protection factors for this type of device were available at the time of going to press. A cautious protection level has therefore been assigned.
There are several organic chemicals within the Isocyanates family and they are found in many industrial applications where two liquid components react to form a solid material. Examples are two-pack paints, insulation materials (e.g. cavity wall), polyurethanes and various coating. Most of these materials are toxic and can provoke severe allergic reaction in sensitised individuals. Occupational Asthma is common in workers who have been exposed even to very low levels and there is a possibility some or all may be carcinogenic. For this reason Isocyanates have a very low exposure limit, and it is vital that exposures are kept as far as possible below this limit.
Although Isocyanate particulate and vapour is readily filtered by AP3 class filters, the substances have very poor warning properties, so there fore a worker may be unaware that their filter is exhausted and omit to replace it when necessary. For this reason, the only filtering respirators likely to be suitable for protection against Isocyanates are full facemasks with A2P3 canisters. These should only be used either for short term escape from a limited spillage or leak, or for short periods where the contaminant concentration is known to be less than 10 X the Exposure Limit (MEL in UK). For general exposures less than 10 X the Exposure Limit, suitable air fed equipment with an APF of at least 40 is generally preferred. For general exposures greater than this, positive pressure demand breathing apparatus should be used, possibly with an auxiliary A2P3 filter to allow transit to the airline connection point (if applicable).
Disposable filtering facepieces, half mask respirators and powered respirator systems are not ideally suited for the control of Isocyanate exposure, so should not be used, unless exposure levels have already been controlled at source to well below the control limit.
The term solvent includes a huge variety of organic liquids used in many applications, particularly pants, coatings, agricultural sprays and cleaning materials. Some are relatively innocuous, albeit sometimes with a fairly strong odour, others are toxic, with possibility of permanent organ damage or carcinogenicity. Many solvents are relatively volatile organic liquids which can be filtered with A type filters, however there are several commonly found substances, e.g. Acetone, Dichloromethane, Diethyl Ether, which are so volatile they may require either an AX type single use filter, or indeed may not be filterable at all.
It is vital in the assessment the airborne concentrations of all solvents in any mix is determined, and the filter types are individually checked.
Because solvents are usually physically absorbed by charcoal filters rather than chemically absorbed, the volatility has a major effect on the filter performance. Also, being volatile, solvents can often be found in surprisingly high concentrations in a work area, meaning that filter life will be correspondingly short. For example, during a painting operation with a toluene based paint in a relatively small, poorly ventilated room, levels of toluene vapour were measured in excess of 500 ppm, meaning that a typical A1 filter cartridge would be unlikely to last more than 2 or 3 hours before saturation. The level of ventilation is vitally important here, since it is relatively easy with even very simple extraction or air management to reduce contaminant concentrations very significantly. Again it is important that this is all properly assessed, as relying on taste or smell to determine filter life may not be safe. This is doubly important if powered respirators are being considered, since although they are usually available with efficient vapour filters, the life of these is rather shorter owing to the high airflow.
E MATERIALS WITH NO SET EXPOSURE LIMIT
There may be substances for which there is not a statutory exposure limit; this is, for example, increasingly true of carcinogens. In these cases, it is usually necessary to set an internal control level, and unless there is good reason to do otherwise, this level will usually be the lowest detectable concentration using modern detection equipment. Some substances may not be easy to detect, and in these cases, the philosophy should always be to reduce exposure as far as is practical.
Generally, control at source of carcinogenic substances should be designed to achieve these low levels, with RPE used solely as the last resort. It would still be advisable, however, in this situation, to select the highest protection RPE compatible with the task and the wearer(s).
Working in confined spaces requires special care and procedures.
Confined spaces are many and varied and commonly include spaces which:
. have restricted means of entry or exit;
. are not intended as a regular workplace;
. are at atmospheric pressure during occupancy;
. could have inadequate ventilation and/or an atmosphere which may become contaminated or oxygen deficient.
Hundreds of workers die every year working in confined spaces pointing to the fact that this is an area that requires special care and training. Courses on working in confined spaces are run by many reputable training organisations. These typically last a week. These courses cover the full spectrum of confined spaces working; these notes are intended as an aide memoir to fully trained operatives and do not represent a full and formal working protocol.
There are basically four types of risk when working in confined spaces; oxygen deficiency, explosive atmospheres, toxic vapours and gases and physical hazards.
Confined spaces occur in almost every industry. Examples would include storage tanks, sewers, cold store rooms, vaults, ducts, boilers, basements, manholes and ships holds. An open ditch or open topped vault can become a "confined space" if air circulation is poor and gases, heavier than air, can accumulate where air does not circulate.
Before any work commences there must be a full plan for the specific confined space entry. This planning can be summarised under six headings:
1. Permit to work
This must be issued by a competent person and cover the task to be carried out, all the safety measures to be observed, the limitation of the permit (location, plant, time etc.), the method for the work to be carried out, the type and amount of safety equipment required for the task, and the emergency procedures to be followed should and accident occur. Should it prove impossible to complete the task within the confines of the issued permit to work then a new one should be issued.
2. Selection of equipment for confined space working
The equipment provided must be suitable for the hazards likely to be encountered, must be fully tested prior to entry and wearers/ users must be fully trained in its use.
3. Rescue plans and considerations
These must be formulated within the permit to work, consider all the potential hazards and include contingencies for each. During any rescue the potential hazards must continue to be monitored to minimise risks to the rescuers.
4. Rescue equipment selection
The equipment selected must enable rescue from all the hazards and contingencies covered in the rescue plan. Potential rescuers must be fully trained in the use of the equipment, which must be fully tested prior to starting work in the confined space.
5. Training for confined spaces
All personnel working in a confined space must be trained to monitor and recognise potential hazards, know the correct and safe working practises and be fully trained in the use of any equipment provided. Within the organisation it is vital that there are personnel trained in both the selection and care and maintenance of the equipment used when working in confined spaces.
6. Emergency procedures
When working in confined spaces there must be a clearly defined and fully circulated emergency procedure such that, should an accident occur, all personnel know the procedures to follow.
