Selection of protective clothing against chemical and biological hazards
Where chemical exposure cannot be prevented by other means, individual protection measures including PPE needs to be applied [2]. Chemical protective clothing (CPC) should be selected to reduce the hazardous exposure well below the danger level. The aim is that the exposure is not at the statutory occupational exposure level, but at a level which the employer can trust to be safe for the employee. For protection, only PPE that has a CE-mark should be used.
The first choice to be made is the clothing type. The types are categorised in accordance to the leak tightness and the structure of the clothing (Table 1). Second, the resistance to permeation or penetration by chemicals has to be considered. The clothing also needs to be of adequate mechanical strength to suit to the task to be carried out. Maintenance and user comfort must not to be overlooked. Many CPC materials catch fire easily. If this risk is present, the CPC needs to be selected accordingly. If the risk posed by the chemicals used concerns only a part of the body, the CPC can be selected to protect only that part of the body, e.g. arms. For such CPC, the letter marking PB (partial body) is added after the marking of the type. The CPC can be meant for limited use (or single use) or they can be reusable. The requirements for reusable CPC are usually stricter than for CPC for limited use [7].
One CPC product often represents several types. It is common that type 3 protective clothing is also a type 4, 5, and 6 clothing, and also clothing protecting against biological hazards and radioactive contamination.
Type 1 CPCs, gas tight suits, are divided into several sub-types. Type 1a has a breathable air supply inside the chemical protective suit. The air supply can be e.g. self-contained open-circuit compressed air breathing apparatus. In type 1b the breathable air supply is worn outside the CPC. In type 1c, a positive pressure of breathable air can be provided via air lines [13]. Types 1a-ET and 1b-ET are meant for emergency teams [14]. Type 1 CPC may be needed for example against dimethyl sulphate, ammonia, chlorine, cyanogen chloride, hydrogen cyanide, sulphur mustard, or Sarin.
Figure 2: Pictogram for chemical protective clothingThe leak tightness for type 1a, and for types 1b in which the facemask is permanently joined to the suit, is ensured with a test that measures how pressurised air is held by the suit. Type 1b suits which have facemasks that are not permanently joined to the suits have to be tested with the same pressure test but also inward leakage test. The inward leakage shall not be greater than 0.05% when measured in the ocular cavity of the mask. Inward leakage test is also used for type 1c and type 2 suits.
Type 2 CPC are not gas tight and a positive pressure of breathable air is provided into the suit e.g. via air lines. The suits can be used against aerosols, sprays or gases, for instance in the manufacture of drugs or other hazardous materials, if the task requires that the employee stands still [13].
Type 3 CPC (and PB) has liquid-tight connections between different parts of the clothing. The CPC can be used in tasks where the contaminants are not air-borne, chemicals may splash under pressure, or the work space is confined and the employee has to lean on contaminated surfaces. The type 3 CPC is not tested for leakage of a gas or particles, but it is tested for leaks by compressed jets of water [14]. The materials can be the same as those used in type 1 or 2 CPC.
Type 4 CPC (and PB) has spray-tight connections between different parts of the clothing. The CPC can be used in tasks where the contaminants are not air-borne, there is a risk of small splashes of chemicals, and the work space is not confined. The type 4 CPC is tested by spraying it with water [16][2]. The materials can be the same as for the type 5, but the seams are taped.
Type 5 CPC is intended for use against air-borne solid particles. It is often used to lessen the respiratory exposure such as those encountered in asbestos work and other tasks with hazardous dusts. The leak tightness of the suit is evaluated through two criteria.
Figure 3: Pictogram "Manufacturer's instructions have to be consulted Source: standard EN 13982-1 [15]One special test is for the total inward leakage (TIL), i.e. the overall mean penetration through the suit while worn by test persons in sodium chloride aerosol atmosphere. The TIL can be used as laboratory based efficacy measure for the CPC. For the type 5 CPC the TIL has to be less than 15% for 8 test persons out of 10 [15]. This is a factor to be seriously considered while selecting the type 5 clothing against hazardous chemicals.
Type 6 CPC (and PB) is meant for tasks where limited protective against liquid chemicals is needed. The overall efficacy of the clothing is tested with a similar spray test as used in type 4 CPC, but with only 10% of the liquid load [17]. The material efficacy against chemicals is measured in percentages, while the types 1–4 are classified in units of micrograms per square centimetres. The type 6 CPC should be only used against small and rare splashes of irritant substances.
CPC has several markings e.g. standard number, type, size and pictograms (Figure 2 and Figure 3).
The first marking means that the clothing is for protection against chemicals and the latter marking means that one must adhere to the manufacturer's instructions.
Leak tightness and resistance to permeation against hazardous chemicals are the two basic factors in selection of the CPC. Chemical permeation tests are required for types 1–4 CPC. The measure of chemical permeation is breakthrough time. It is the time elapsing between the initial application of a test chemical to the outside surface of a protective material and the time when the permeation rate through the material exceeds 1,0 µg x min-1 x cm-2 or 0,1 µg x min-1 x cm-2 [18]. The breakthrough time is always specific for the pair: CPC material and chemical. Generalising the breakthrough times for materials types with the same material names is common, but this should be done with great caution, since the breakthrough time is not necessarily the same for the materials with the same names.
EN standards require the breakthrough times to be reported as protection classes (Table 2).
Table 2: Protection classes for chemical permeation and corresponding breakthrough times
Protection class Breakthrough time, min 1 10 - 30 2 30 - 60 3 60 -120 4 120 - 240 5 240 - 480 6 over 480
Source: EN 14325 [19]
Breakthrough time is not same as the safe usage time of the clothing. Breakthrough times can be used in comparing several products and also as a warning about totally unsuitable products. The efficacy of the selected clothing has to be always related to the risks involved in the task.
Types 1a-ET and 1b-ET have to be tested against permeation of 15 chemicals that are listed in the standard EN 943-2 [14]. The test chemicals represent a wide range of aggressive chemicals. Thus, the clothing that meets the requirements according to this standard, will offer protection against a wide range of chemicals. If the breakthrough time for those solvents, gases, acids and bases is not over 30 min, the instructions for use must clearly state that this CPC does not offer protection against continuous exposure to the chemical.
In the test for chemical penetration, a small quantity of liquid is dispensed onto the surface of the protective clothing material, which is laid in an inclined gutter at an angle of 45°. The liquid is allowed to run off and the quantity that penetrates the material is measured. The type 6 CPC (and PB) will fulfill its requirements, if for one test chemical of those that are listed in the standard EN 13034, the penetration is less than 5%. The chemicals are sulphuric acid (30%), sodium hydroxide (10%), o-xylene, and butan-1-ol [17][20] Other test chemicals can also be used.
CPC must possess minimum performance requirements for mechanical strength. In laboratory tests preceding the EC type examination of types 1–4 clothing, the following mechanical properties are assessed:
The same properties are measured and classified for the CPC types 5–6 with the exceptions that the tensile strength for type 5 and flex cracking for type 6 are not essential [15][17].
The results of the assessment are given as protection classes in the CPC's instructions for use. Each class can be used in a comparison between different CPC. The larger the number of the protection class the better is the clothing with respect to that property [19].
In the ignition test of the CPC, a flame is passed over the surface of the material. The material should not form droplets and should prove to be self-extinguishing [21]. Passing this test does not mean that the CPC would not burn in fire. This requirement must be met for CPC of types 1, 2, 5, and 6.
The statutes state the workers' exposure to biological hazards must be prevented. Where the exposure cannot be prevented by other means, individual protection measures including PPE must be used. Workers have to be provided with appropriate protective clothing or other appropriate special clothing [4].
According to the standard EN 14126 protective clothing against biological hazards is classified into the same types of leak tightness as chemical protective clothing [12]. As a way of recognizing the clothing, the suffix B is added, e.g. type 3-B. The pictogram "protection against biological hazards" is also used (Figure 4).
The clothing materials are tested for resistance:
In the selection of the protective clothing, one should be note that the efficacy offered by the protection class 1 is not very high. The larger the number of the protection class, the better is the clothing for that specific property.
Working in impermeable protective clothing has significant effects on the thermal load generated by its users. The clothing limits heat and moisture transport and this leads to elevation of skin and core temperature. This can result in various health effects ranging from transient heat fatigue to serious illness, even death. The type of the clothing and its ventilation, the work activity, climate conditions, and the characteristics of the wearer of the clothing all influence the development of the heat stress [7][9][9]. CPC types 1–3 are made from impermeable materials, types 4–6 may also be made of microporous materials, but only type 6 materials can be breathable.
The physical performance of the users has to be examined before starting the occupational use of leak tight protective clothing and periodic examinations have to be conducted. Spiroergometry is used to evaluate Finnish chemical emergency rescuers [22].
The tasks need to be planned with care. The clothing user needs rest breaks. If the environment is hot and work load is heavy, the working time may have to be limited e.g. 20 min. The user should be monitored for physiological factors such as heart rate, temperature, and body water loss [9].
Protective clothing against chemical and biological hazards makes it more difficult to carry out the work, but the hindrance should be as small as possible. Comfortable work conditions make the work more efficient, and thus efforts should be expended in the selection of the clothing. The user has to be able to perform all the movements, assume the working positions he or she will have when performing the work, and be able to use the working tools. In order to ease the work load the clothing should be selected so that its donning and removal are easy. The removal has to be straightforward also since different kind of emergencies may arise, and the clothing may need to be taken off quickly. A poor fit of the clothing may result in reduced efficacy of the clothing [7][9].
If other PPE are needed together with the protective clothing, the efficacy of the entire PPE has to be ensured. Special care has to be taken to ensure that the wearer, who has to wear hearing protection will be protected and be able to communicate and hear warning signals. Difficulties may also arise in combining gloves, footwear, respiratory mask, and eye shields so that they are tight enough. When using protectionagainst fall from heights, attention should be paid to the mechanical strength of the protective clothing.
Workers have the right to be consulted over the selection and purchase of protective clothing. Wearer trials are needed to ensure the usability of the protective clothing. An evaluation of the maintainability of the clothing is also needed before the selection.
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