fit PIRATIRS AND BREATHING APPARATUS

Transcription

1 YI fit PIRATIRS AND BREATHING APPARATUS

2 RESPIRATORS AND BREATHING APPARATUS Occupational Health Series No. 2 First Issued 1956 Revised Occupational Health and Toxicology Branch Department of Health New Zealand 1984

3 The Department of Health wishes to express thanks to the following organisations for their assistance in the production of this booklet: 3M NZ Limited Department of Labour Martin Equipment Limited Martindale Electric Co. Limited New Zealand Safety Limited Protector Safety Limited Wormald Stero Safety Limited

4 CONTENTS Page Introduction 5 1 General Principles of Respiratory Protection 7 2 Classification of Inhalation Hazards 9 - Particulate contaminants - Gaseous or vapour contaminants - Oxygen deficiency 3 Factors to Consider when Selecting Respirators 11 4 Types of Respirators 13 5 Air Purifying Respirators 15 - Particulate respirators - Gas respirators - Combination respirators - Powered air purifying respirators 6 Airline Respirators 23 - Fresh air hose respirators - Compressed airline respirators - Precautions for normal use 7 Self-contained Breathing Apparatus 27 8 Practical Considerations 29 - Issuing - Instruction - Face fitting - Checking effectiveness - Supervision in a dangerous atmosphere - Location 9 Maintenance 31 - Inspection - Cleaning - Storage 10 Respirators for Aircrew involved in Aerial Spraying 33 APPENDICES I Standards for Respirators II Examples of Agriculture Chemicals used in Aerial 37 Spraying

5 INTRODUCTION This booklet examines some common hazards against which respiratory protection is required, and gives guidance on the selection, use and care of respirators. It is not possible to set out precise requirements for every industrial situation where there is an inhalation hazard because the factors which have to be considered vary considerably from one work place to another. However both the supplier and the user should be satisfied that the equipment selected is adequate for the conditions. If there is any doubt you should seek technical advice from the Departments of Health or Labour.

6 1. GENERAL PRINCIPLES OF RESPIRATORY PROTECTION 7 Breathing air which contains toxic substances or air which has insufficient oxygen to support human life is a very real and common hazard in industry. The aim is to work in air that is clean and safe, and there are 4 ways this can be done: avoid atmospheres containing toxic or irritant substances avoid using toxic or irritant materials totally enclose the process install an adequate ventilation system. An efficient exhaust ventilation system removes contaminated air from the workplace so a respirator is not required. In emergencies or general situations where these principles cannot be applied a respirator must be worn. Some substances irritate the eyes and skin, others can be absorbed through the skin as well. Anyone entering an atmosphere containing materials with these properties needs more than just respiratory protection, their whole body should be protected.

7 2. CLASSIFICATION OF INHALATION HAZARDS 9 Respirators are designed to protect against 1 or more of the following types of atmospheric hazards: - Particulate contaminants - Gaseous or vapour contaminants - Oxygen deficiency PARTICULATE CONTAMINANTS Dusts These are solid particles dispersed in the air and may be respirable or non respirable. Respirable dust consists of tiny particles less than five thousandths of a millimeter (5 microns) in size. They are invisible to the unaided eye and are fine enough to penetrate the finest airways in the lung. Non respirable dusts are larger in size and are removed in the nose or upper airways of the lungs. Respiratory protection is required for three different categories of dust: Nuisance dusts - these irritate the nose and lungs but are not toxic and don't damage the lungs. They pass out of the body or remain in the lungs without poisoning the system. Examples are calcium carbonate (limestone dust) starch, cement dust, and sucrose. Lung damaging dusts - respirable particles of these dusts remain in the lungs where they may damage the tissue. For example, asbestos, crystalline silica (quartz dust) and coal dust. Toxic dusts - these pass from the lungs into the blood and may poison the whole body. For example, lead, arsenic and powdered organophosphate pesticides. Mists These are fine droplets of liquid dispersed in the air and may contain particles or dissolved substances. Mists are produced by condensation of a vapour or by atomisation of a liquid. Examples are paint spray and chromic acid mist from an electroplating bath. Metallic Fumes These are fine particles of metal produced by condensation of the vapour given off by a metal when it is subjected to high temperatures, for example, during welding and smelting. GASEOUS OR VAPOUR CONTAMINANTS Gases A gas is a substance that is in the --us state under normal conditions of temperature and pressure. There are 2 categork which different types of respiratory protection is required:

8 10 Acid gases, eg, hydrogen chloride and sulphur dioxide. Alkaline gases, eg, ammonia and diethylamine. Vapours A vapour is the gaseous form of a substance that is a solid or liquid under normal conditions of temperature and pressure. Examples are, organic solvents such as benzene and trichiorethylene, and inorganic substances like lead, cadmium and mercury. OXYGEN DEFICIENCY Normal air contains 21 percent oxygen, but this may be reduced by a chemical reaction or by displacement. There is often a lack of oxygen in tanks, vats, reaction vessels, wells, tunnels, silage pits, sewers and deep earthern trenches. When the oxygen level falls below 17 percent special precautions must be taken and a supply of fresh air arranged for anyone entering the danger area.

9 11 3. FACTORS TO CONSIDER WHEN SELECTING A RESPIRATOR What is the nature of the hazard? -particulate, gas or vapour, oxygen deficiency, or a combination of these? What is the concentration of the contaminant? What warning signs does the contaminant give? How long will the person be in the contaminated atmosphere? How acute is the hazard? (Will failure of the device for a short time cause serious harm?) How far away is the contaminated atmosphere from the nearest uncontaminated air? What is the access to and the nature of the working environment? What job is to be done in the contaminated atmosphere? How easy is movement in the contaminated atmosphere? Is a respirator for regular use or only for emergency or rescue purposes? If you have any doubts as to the correct device for a particular situation you should seek expert advice from the Department of Health or other authority on industrial hygiene.

10 13 4. TYPES OF RESPIRATOR From the user's point of view and the type of working conditions, respirators can be grouped into 3 major types: Air Purifying Respirators These respirators draw inhaled air through a filter that removes harmful gases or particles. They do not give protection against a lack of oxygen and should only be used when the type and concentration of the contaminant is known. Airline Respirators These use an airline to supply clean air from a source outside the contaminated area. Clean air can be supplied either at normal atmospheric pressure or at a higher pressure eg, a compressed air supply line. Self-contained Breathing Apparatus (SCBA) This respirator uses an airline to supply clean air from a source that is usually carried by the wearer, eg, compressed air bottles. Self-contained breathing apparatus is used to give protection against dangerous breathing hazards such as a lack of oxygen, very poisonous contaminants, or when the type of hazard is unknown. A more detailed description of these 3 major types of device is provided in the next three sections. There are 2 clear uses for most types of respirators: 1 Regular work use 2 Emergency use. Different selection criteria should be used for each of these.

11 15 5. AIR PURIFYING RESPIRATORS Reusable air purifying respirators have a moulded rubber or plastic face piece which is held snugly against the skin by straps or a harness. They have a replaceable filtering device such as a cartridge or a canister. Disposable or non-renewable respirators are mostly or entirely made of filter material and are discarded once the filter or sorbent is no longer useable. They have the same function as reusable respirators. Disposable respirators and cartridge or canister filters should be replaced: - when the life of the device has elapsed (as recommended by the supplier) - when difficulty in breathing is experienced - when the wearer detects the taste or smell of the contaminant. There are 3 types of face piece: 1 A quarter face piece which covers the mouth and nose only, 2 A half face piece which covers the mouth, nose and chin. 3 A full face piece which covers the whole face from chin to hair line and from ear to ear. If protective goggles or prescription glasses are worn, a respirator that uses a quarter or half face piece may interfere with them. This problem can be avoided by wearing a full face piece, a hood, or a helmet respirator instead. Prescription lens glasses can be incorporated into some types of full face piece. Limitations on the normal use of air purifying respirators - The device selected must be suitable for the contaminant encountered. - The contaminant must be below the maximum concentration for which the device is suitable. - Air purifying respirators should not be used in areas where contaminants present an immediate danger to life and health. - Do not use these respirators in atmospheres that may be deficient in oxygen. There is no universal colour code for canisters and cartridges. British, American and German manufacturers have their own individual systems, and cartridges, canisters and filters from these sources are available in New Zealand. It is therefore most important to make sure that the cartridge, canister or filter is positively identified as being suitable for a given situation and that you do not depend on a colour code. It is the supplying company's responsibility to ensure this information is given correctly.

12 16 HEAD HARNESS CIv NOSE CANISTER CONNECT IN H A LAT I VAL EX HA LAT VALVE EXAMPLE OF A FULL FACE PIECE FACE PIECE CAR F I Li I NSI HEF EXAMPLE OF A HALF FACE PIECE 1

13 17 PARTICULATE RESPIRATORS These filter finely divided solid or liquid particles from the air, ie dusts, mists and fumes. The wearer's normal breathing action draws contaminated air through a filter, usually a fibrous material, and the contaminant particles impact and are trapped on the filter fibres. In some filters, the fibres are treated with an electrostatically charged resin which helps trap the contaminating particles. A problem with these is that exposure to heat or high humidity causes the charge to be lost and reduces the filtering efficiency. A half face piece respirator with cartridge filters for particulate contaminants.

14 18 The degree of protection depends on the type of filter and the effectiveness of the individual facial seal Those with a low filtering efficiency are satisfactory for use with a nuisance dust or a dust of low toxicity, while particulate respirators with medium filtering capacities should be used where protection from more toxic particulate contaminants is required, eg, in smelting, where metallic fumes are produced. High efficiency particulate respirators usually have a full face piece which guarantees an effective facial seal to prevent highly toxic or irritant particulate contaminants leaking into the respirator. This type of device is used when handling highly toxic dusts or powders, like organophosphate insecticides and radionuclides. In particularly heavy concentrations of dust, eyes need protection by using a full face piece, a hood or a helmet respirator. Where a high dust concentration causes the filter to clog; or when the job does not require great mobility, an airline respirator can be used. (See section 6.) A disposable respirator giving protection against wood dust.

15 19 A full face piece respirator with cartridge filters is used where there is toxic vapour. GAS/VAPOUR RESPIRATORS These respirators use a filter containing an agent which absorbs or reacts with the contaminant gas or vapour. There are 3 types of gas/vapour respirators: - half face type (usually takes a cartridge) - full face type (usually takes a canister) - disposable type (filter built into the face piece) Cartridge respirators and some disposable respirators are suitable for low levels of certain gases and vapours*. Canister respirators and some disposable respirators are suitable for higher levels of certain gases and vapours*. * Your supplier should provide detailed information about the relevant gas/vapour and the level against which each type will provide protection.

16 20 Full face mask respirators can cope with higher levels of gases/vapours because of their superior face sealing characteristics, and they provide eye and face protection as well. The life of a canister, cartridge, or disposable respirator in use depends on the concentration of the contaminant, the humidity and the work rate of the wearer. NB When not in use, cartridges and canisters should remain sealed or in airtight containers or bags to prevent the 'reacting agent' from deteriorating on exposure to the atmosphere. A full face piece respirator with canister filter. COMBINATION ATION itespira'l'ors (ie, particulate and gas/vapour) Where there is a combination of particulate (ie, dust, mist, fume etc) and gas/vapour contaminants, a dual purpose filter, cartridge, or canister can be used. Particulate filters or disposable respirators impregnated with a reaction agent to remove vapours in low concentrations are available.

17 21 For half and full face respirators, the canister or cartridge can either have an in-built particulate pre-filter or a pre-filter attachment. POWERED AIR PURIFYING RESPIRATORS These have a battery powered blower/fan unit which helps air pass through the filtering medium to the facepiece (half facepiece, full face piece, helmet, hood etc). The positive pressure effect created by the 'powered air' in the facepiece area reduces the possibility of inward leakage and increases comfort.. They are particularly suitable for people with a beard or moustache since facial hair reduces the effectiveness of the face piece seal in standard 'negative pressure' respirators. Powered air purifying respirators may be fitted with filters, cartridges or canisters which remove particulates, gases or vapours. The criteria for selecting these filters are the same as those for other air purifying respirators. The positive pressure effect of a powered air purifying respirator is particularly suitable for workers with a beard or moustache.

18 23 6. AIRLINE RESPIRATORS There are 2 groups of airline respirators: Fresh air hose respirators - Compressed airline respirators - draw air at atmospheric pressure through an air hose. supply air under pressure through an airline. FRESH AIR HOSE RESPIRATORS Air hose respirators consist of a face piece connected to an air hose which has its free end anchored in an uncontaminated atmosphere. Air at atmospheric pressure is drawn through the hose by normal breathing. The resistance of the hose to the passage of air limits the length of the hose to about 15 metres. All connections should be tight to prevent contaminated air leaking into the airhose. See your supplier for more detailed information. When longer hoses are used air is supplied under slight pressure by a pump, blower or bellows which can be operated by an attendant. Leakage into the apparatus is prevented by a positive pressure effect. The blower should be sited so it supplies clean fresh air. Before the face piece is put on, the blower should be operated rapidly to ensure that dust inside is blown out and clean air is being delivered to the face piece. The ends of the hose should be sealed after use. An air hose respirator provides clear air from a source remote from the contaminated area.

19 24 COMPRESSED AIRLINE RESPIRATORS These consist of an airline from a compressed air source to a breathing tube attached to the wearer. The breathing tube connects with either a half face piece, a full face piece, a hood or a helmet. The flow of air to the half and full face piece types may be either continuous or controlled by a demand valve. The continuous flow of air creates a positive pressure inside the face piece or helmet, which gives greater protection than a demand type respirator. It also reduces fogging and cools the wearer's face. The flow rate can be adjusted by a belt mounted regulator. The demand flow type lets air into the face piece only when the worker is breathing in, which conserves compressed air. Hood and helmet airline respirators are used when the head and neck must be protected. Because the efficiency of this type of respirator depends on maintaining a positive pressure inside the hood, the respirator must fit closely round the neck. Drawstrings or elasticised neckbands should be as tight as comfort allows. It is not enough to tuck the cape or inner bib part of the hood inside your shirt or other garment. Increasing the air pressure above the manufacturer's recommendations will not necessarily increase the protection. In fact, it may create vortex currents and local areas of negative pressure within the hood causing inward leakage of the contaminated atmosphere. Also, the extra noise the wearer is subjected to may be unacceptable. Compressed airline respirators should have an air purifying cartridge filter unit to remove carbon monoxide, and where appropriate a condensate trap in the airline to remove contaminants such as oil or water. A compressed airline respirator protects against the vapour of a pesticide concentrate.

20 25 PRECAUTIONS FOR NORMAL USE All fresh air hose intakes should be supervised to ensure a continuous supply of fresh air. Compressor air intakes should be sited to avoid contaminantion (particularly exhaust gases from internal combustion engines). Don't let the compressor run hot, as decomposition of the lubricating oils may produce dangerous amounts of carbon monoxide and other harmful substances. Remove water and pockets of stagnant air before you use an airline. if the air supply is used in a manufacturing process as well as for supplying an airline, take particular care to avoid contamination. A filter regulator must be used with a compressed airline respirator. Airline respirators provide reliable respiratory protection only if the air supply is continuous and efficient. An airline respirator should only be used in an atmosphere not immediately dangerous to life or health because failure of the air supply will expose the wearer to contaminated air. An exception to this is where the wearer carries an emergency air supply to allow enough time to escape (eg, self contained breathing apparatus). A helmet airline respirator in use during sand blasting.

21 27 7. SELF CONTMNED BREATifiNG APPARATUS - SCBA This type of respirator lets the wearer work without the restriction of a hose or airline in an atmosphere that is contaminated and/or deficient in oxygen. Self contained breathing apparatus are suitable for short term routine work and emergency use. MR J IS2ft.Y tw'- Self contained breathing apparatus can be used in regular work to protect against lack of oxygen or an unknown level of toxic contaminants. 0 I The most widely used SCBA is a compressed air open circuit device with a compressed air cylinder, an airline to a demand regulator, and a face piece. These can be supplied in a positive or negative pressure mode. The air supply may last from 5 to 45 minutes depending on cylinder size. Negative pressure airflow SCBA are prone to leakage through the facial seal and care must be taken in fitting the face piece to minimise this. If the SCBA is operated in a positive pressure mode, leakage is outwards only. The main limitations of these devices is their size, which restricts movement in narrow spaces, and the limited time of the protection afforded. The use of this type of equipment should be restricted to specially trained and experienced personnel. Keep the breathing apparatus in good operating order. The supplying company can advise you on correct and regular service procedures.

22 29 8. PRACTICAL CONSIDERATIONS ISSUING For routine industrial use respirators should be issued on a personal basis. This ensures a correct fit each time a device needs to be worn and eliminates the possibility of infection being transferred from person to person through the face piece. Personal issue helps the wearer know when to replace a cartridge/canister. It is good practice to establish a recording system, stating the date of issue, the person to whom the device has been issued, defects reported, and maintenance that has been carried out. INSTRUCTION Wearers must be taught the correct way to use respirators, and instructions should cover the following: when a respirator should be worn; the importance of using a respirator; the way the respirator works; the limits of the respirator; how to recognise poor performance or improper functioning; the approximate time the respirator will give protection in the particular conditions; what procedure to follow if a fault develops when it is being used. what to do in an emergency the importance of not removing the face piece until the wearer is certain that there is no longer any hazard; how to store the respirator correctly; how to clean and maintain the respirator. Training should include wearing the device in a suitably contaminated atmosphere as this gives confidence with the device. FACE FITTING Where facial irregularities or hair interfere with the face seal, a positive pressure device should be considered. The manufacturer's instructions about checking the effectiveness of the face seal should be followed.

23 30 CHECKING EFFECTIVENESS The facial seal of some respirators can be tested by using a strong smelling organic substance of low toxicity. For example, sodium saccharine or banana oil can be vapourised around the face piece seal. If the wearer can't detect the characteristic taste/smell of the vapour, then the facial seal is adequate. 'Vesting devices are available from equipment suppliers. SUPERVISION IN A DAN GEI(OUS ATMOSPHERE Whenever a respirator is used in an atmosphere which might be dangerous on short exposure, such as a tank, vat, pipe or other confined space, a trained assistant should continually be in contact with the wearer. Correct safety procedures for entry into confined spaces are described in the publication "Safety in Confined Spaces" produced by the Department of Labour. LOCATION Respirators should be located as close as practicable to the working place where they may be needed. Emergency equipment should be stored close to the danger area in clearly marked locations so that a rescuer can immediately find it. Emergency respirators stored in a clearly marked site close to the work place.

24 31 9. MAINTENANCE It is important that each respirator is properly maintained and stored. Someone's well-being or life may depend on its functioning and availability. A regular maintenance and cleaning programme and a designated storage place should be established. INSPECTION All rubber parts such as face pieces, mouth pieces, valves, breathing tubes, air hoses, airlines and head bands should be inspected for deterioration such as hardening, cracking or tackiness. Check metal parts for signs of corrosion, and plastic and glass parts for cracking or breakage. Check canisters and cartridges for damage and corrosion. When an air supply system is in use it should be inspected regularly. Air compressors, air cylinder manifold systems, pressure reducers, pressure release valves, airline filters, condensate traps, airline instrumentation and permanent piping and outlet fittings must be kept in good repair to ensure that the air reaching the wearer is uncontaminated. CLEANING Air Purifying Respirators It is essential that the face piece is kept clean for continued efficient use. To do this, remove the canister or cartridge filter units (or hose if fitted) and wash the face piece in warm water and detergent. DO NOT WASH THE CANISTER OR CARTRIDGE UNITS. Brush the face piece if necessary to remove soil. Rinse in clean warm water and air dry. Reassemble and store (see page 32). Disinfectant is not recommended for cleaning the face piece, as it may cause a skin reaction if it is not completely rinsed off. Each time the respirator is serviced, remove the valves and clean them. The valve seats may need to be scrubbed with a small brush. Valves should be washed in cold or lukewarm water only and quickly dried (moisture allowed to dry slowly on them may interfere with their correct functioning). Airline and self contained breathing apparatus Clean the face pieces as described for the air purifying respirators. Hoses should be checked for defects. Compressed air cylinders must be filled from a recognised safe source, such as dive shops. They must be filled, inspected, tested and maintained in accordance with the requirements of the Dangerous Goods (Class 2 Gases) Regulations which are administered by the Department of Labour. Used or partly used cylinders must be recharged as soon as possible after use. Make sure you follow the manufacturer's instructions when servicing self contained breathing apparatus.

25 32 FINAL INSPECTION Carefully check assembled respirators to ensure that all components are in place and that all moisture has been removed from surfaces and crevices. STORAGE Respirators should be kept clean and dry. Keep them away from oil and exposure to direct sunlight, which causes deterioration of rubber parts. They should not be stored in a tool box or clothing locker. A dry box or cupboard is satisfactory. Face pieces should be stored so that they are not subject to distortion. Do not hang the respirator by its straps as this causes them to stretch, resulting in a poor facial fit. If face pieces are not used very often, store them in plastic bags to protect them from dust and corrosive atmospheres. It is a good idea to store canisters in sealed containers bearing the date of the last inspection.

26 RESPIRATORS FOR AIRCREW INVOLVED IN AERIAL SPRAYING Pilots may be exposed to dusts and mists from agricultural chemicals used in aerial spraying. If there is a risk of inhaling toxic material, appropriate respiratory protection should be worn. An appropriate particulate respirator should be worn if a pilot is exposed to spray drift or dusts which cause irritation to the mucus membrane lining of the upper or lower respiratory tract. Where the pilot (or ground crew) is exposed to spray drift of materials which have an oral L.D.50* of less than 150 mgm/kg in the most sensitive animal tested, an appropriate particulate respirator should be worn: - Where the L.D.50 of the material is between 50 and 150 mgrn/kg (moderately toxic) respiratory protection may be adequately provided by a cartridge type respirator with a half face piece.the cartrid ge must offer appropriate protection against toxic mists, organic vapours or dusts, as required. - Where the L.L).50 of the material is less than 50 mgm/kg (high or very highly toxic) a high efficiency respirator should be used. This would normally have a full face piece, and use a canister which effectively protects against toxic mists, or vapours as required. The face piece and canister should meet any one of the standards given in Appendix 1. The ground crew may also be exposed to pesticides while helping with loading, and from spray drift. They should also take the appropriate respiratory protective measures outlined in this booklet. * The L.D.50 of a substance is the dose that is calculated to kill 50% of a test population of animals.

27 35 APPENDIX I Standards for Respirators British B.S B.S B.S B.S B.S B.S German D.I.N D.I.N D.I.N USA Code of Federal Regulations Part II subparts A to M. Australian A.S A.S NZ NZSS 2209 NZSS 2266 Accept equipment tested to ANSI and CEN standards when these are established.

28 37 APPENDIX II Examples of Agricultural Chemicals used in Aerial Spraying An indication of the need for respiratory protection as determined by the level of toxicity of the chemicals is given below. INSECTICIDES Major Trade Active Name Ingredients Lannate Tamaron P hosdrin Lorsban F enitrothion L indane M etasystox Pirimol Ambush Sumicidin Attack Dicidex Dipterex M alath ion Gusathion Sevin HERBICIDES Methomyl Methamidophos Mevinphos C hlorpyrifos Granules Pirimicarb Permethrjn F envalderate P irimiphosmethyl Trichiorphon Trichiorphon Azinphos Carbaryl Formulation Granules or powder Powder or powder or powder or powder Toxicity High High Very high Moderate Low-moderate Moderate Moderate Moderate Low-moderate Low-moderate Low Low Low Low Very high Low Appropriate Respiratory Protection Required Required Required Required Not required Required Required Required Not required Not required Not required Not required Not required Not required Required Not required 24-D 245-T 24-DB MCPA MCPB Buctril Foddercleen Brom oxynil, MCPA Nitrofen and Picloram Low-moderate Not required Low-moderate Not required Low-moderate Not required Low-moderate Not required Low-moderate Not required Low-moderate Not required Low Not required

29 38 Major Trade Active Name Ingredients Appropriate Respiratory Formulation Toxicity Protection Lontrel p. Bromoxynil, MCPA LontrelC MCPB Reglone Diquat Paraquat Asulox Asulam Dicamba 22DPA Tordon Phenoxy herbicides Dicambone 24-D Roundup Glyphosate Ban T Weedazol 41, Amitrole Velpar Hexazinone Krenite Fosamine FUNGICIDES Bayleton Triadimefon Antracol Propineb Ridomil Netalaxyl Kocide Copper Hydroxide Bravo Chiorothalonil Tilt Propiconazole Afugan Pyrazophos Topsin Thiophanate-methyl Benlate Benomyl Sporex Thiophanate-methyl Saprol Triforine Milcurb Dimethirimol BAITS 1080 Malathion Slugbait Methiocarb Powder Powder or pellet Powder Powder Powder Powder Powder or liquid \. Powder Prills Low-moderate Not required Low-moderate Not required Moderate Required High Required Very low Not required Low Not required Low-moderate Not required Low-moderate Not required Low-moderate Not required Very low Not required Moderate Not required Low Not required Low Not required Very low Not required Low-moderate Not required Very low Not required Low Not required Low Not required Very low Not required Low Not required Moderate Required Very low Not required Very low Not required Very low Not required Very low Not required Low Not required High Not required Low Not required Low Not required

30 OTHER PUBLICATIONS IN THE OCCUPATIONAL HEALTH SERIES ARE: Diseases Arising From Occupation Eye Protection OHS No 3 4 Occupational Dermatitis Hearing Conservation Notes on Occupational Health Nursing Poisons and Poisoning Motor Garage Hazards Agricultural Health Plastics Fumigation Laboratory Safety Occupational First Aid Occupational Health Services in New Zealand The Rubber Industry Working with VDUs (Pamphlet) Working with isocyanates (Pamphlet) isocyanates: Medical and Technical Data Occupational Health Series No. 1 has been withdrawn. When booklets in this series are considered for reprinting the text is revised and updated. This may mean that some booklets are temporarily unavailable. Department of Health New Zealand Code 4749 P. D. Hasselberg, Government Printer, Wellington, New Zealand J bks/1/84PTK

31 I '. T NZ OCCUPATIONAL HEALTH SERIES NO. 2 ISSUED BY THE N. Z. DEPT. OF HEALTH CODE 4749