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Work environments ranging from large petrochemical complexes to small retail stores present a vast variety of hazards, resulting in a nearly a million work related injuries and illnesses every day across the world.
The International Labour Organization published this devastating statistic in 2009, and unfortunately, the situation is not getting any better.
Exposure to hazardous chemicals is a frequent contributor to the above statistics. Many chemicals are known to be harmful to health and can be easily absorbed into the body. Chemicals mainly enter the body through the respiratory tract and the skin. In all cases, uncontrolled exposure can lead to unpleasant consequences ranging from contact dermatitis to fatality.
In order to minimise a worker’s contact with chemicals, employers implement engineering, administrative and work practice controls; however, where such controls are inadequate, chemical protective workwear is used to prevent exposure and provide the last line of defence.
This article is about chemical protective workwear used in workplaces during both routine chemical management and non-routine activities such as spill response, waste handling or rescue operation in case of emergencies. It discusses the use of chemical protective workwear, its selection and testing requirement, maintenance and storage aspects.
The need for chemical protection
Chemical protective workwear, as any other personal protective equipment (PPE), is the last resort in the hierarchy of control. It should be considered only when all other means of protection are ruled out, as demonstrated through a task specific risk assessment. As an example of avoiding direct exposure, removal of contaminated sludge from a tank should be achieved by using a vacuum truck and cleaning the traces with a hydro jet machine with a rotating nozzle inserted from the top manway of the tank. This will prevent workers from entering the tank and removing sludge by shovelling – a method that is still being practiced in many countries.
Clearly engineering controls are preferable, but not always feasible or available. A good example could be emergency response activities involving chemical leaks and spills. In a plant or warehouse environment, spills could be contained and removed by the provision of drains directed to a treatment unit, but there is no way to clean up a chemical spill on a public road without manual intervention.
Containment and clean-up activities will require workers to wear suitable chemical protective workwear, which should typically be worn with respiratory protective equipment.
Appendix B of OSHA HAZWOPER standards (29 CFR 1910.120) provides specific requirements on the level of protection necessary, depending on the work environment and hazards involved.
OSHA outlines four protection levels:
1. Level A is the highest available level of respiratory, skin and eye protection. This usually includes fully encapsulated suits and should be used in highly hazardous work environments, including sites containing asbestos, and volatile toxic chemicals. It is also used for operations conducted in confined and poorly ventilated areas, which can increase the risk of exposure.
2. Level B offers the same level of respiratory protection, but less skin protection than Level A. Level B should be used only when the vapour or gases present are not suspected of containing high concentrations of chemicals that are harmful to the skin or capable of being absorbed through intact skin.
3. Level C allows the use of air purifying respiratory protection and offers limited skin protection.
4. Level D offers no respiratory protection and minimal skin protection.
Selection and testing
Once the level of protection is identified, the next step is to select the suitable clothing and equipment to achieve the desired protection level. It is of paramount importance to understand that no chemical protective workwear can provide protection against all hazards. Each item of chemical protective workwear has its intended purpose and limitation, and should be used only for tasks for which it is designed.
The following are some important considerations when selecting chemical protective workwear:
1. Although the use of ‘impervious’ clothing is frequently recommended, such clothing does not exist. All commercially available chemical protective workwear tested will allow some chemicals to permeate in relatively short times.
2. Because all chemical protective workwear is vapour resistant, evaporative cooling of the skin is prevented. This leads to an increase in the skin’s temperature and moisture levels during the use of the chemical protective workwear. Under such conditions, it can be difficult to detect if a chemical has permeated unless sensory effects such as itching, discolouration, or burning occur. Even after the chemical protective workwear is removed, an exposure may not be recognised if an odour is not noticeable or the skin appearance has not changed. Furthermore, the warm, humid conditions under the chemical protective workwear can increase the permeability of the skin.
3. The same thickness of a generic material, such as neoprene or nitrile, supplied by different manufactures may provide significantly different levels of protection because of variations in the manufacturing processes or in the raw materials and in the additives used in processing.
The specific type of chemical protective workwear should be selected after detailed workplace and activity evaluation. This may include systematic job review or analysis techniques such as an industrial hygiene survey, job safety analysis, or fault tree analysis, which can be used to determine the potential for chemical contact and the conditions that chemical protective workwear must withstand.
Information should be collected to answer the following specific questions for the selection of chemical protective workwear:
1. What is the composition of the chemicals and chemical mixture used in the workplace? A list of all chemicals and their concentrations contained in a product or utilised should be obtained from the Safety Data Sheets (SDS), container labels, or manufacturer’s product literature.
2. What are the state and properties of the chemicals used in the workplace? If a chemical is present as a vapour and the vapour exposure can be harmful, the worker should use whole body protection, such as Level A protection.
3. Is the chemical contact limited to an occasional accidental splash, with the opportunity available to quickly change the chemical protective workwear? Or is the chemical protective workwear in continuous contact with the chemical for long periods of time?
4. If chemical protective workwear is to be removed after a short exposure time and then donned for another subsequent exposure time, might the worker be exposed as the result of handling, doffing, and donning the contaminated workwear?
5. What is the temperature of the environment in which chemical contact may occur? With each 10°C rise in temperature, the permeation rate roughly doubles and breakthrough time significantly decreases. Is there potential contact with open flame or will high environmental temperatures be encountered? Many chemical protective workwear products are flammable.
6. What parts of the body can the chemical potentially contact? Some types of garments such as boots are available only in a few generic materials.
7. Will the chemical protective clothing be used in a workplace where abrasions, cuts, punctures, or tears may occur? Requirements for laying down an absorbent pad on the spill are different from those working in confined space with sharp edges, hence endurance requirements for workwear will differ.
8. Does the work include delicate tasks that require high manual dexterity? Could the workwear catch on moving equipment to cause an injury? Is the work environment prone to causing heat stress, particularly if large areas of the body are covered with a vapour barrier of workwear?
Once all above questions are answered, you can start looking at different products available on the market and select the most suitable one. Again, there is no simple criterion that would allow you to pick a product by a brand name, material or protection feature. Each manufacturer is obliged to perform tests, which should demonstrate the performance and quality of their product, hence a review of the product data sheet and associated literature will help in decision making.
The following are important parameters that should be considered when selecting the chemical protective workwear.
Permeation Permeation is the absorption, diffusion, and desorption of a chemical through the barrier material at the molecular level. Permeation should not be mistaken with penetration. The latter presents the flow of a chemical through closures, porous materials, seams, pinholes, or other imperfections in a protective workwear material on a non-molecular level. The key measures include breakthrough time and permeation rate, which demonstrate the effectiveness of a clothing material as a barrier to the test chemical. Long breakthrough times and low permeation rates are characteristics of better barriers.
Degradation Degradation is a deleterious change in one or more physical properties of a protective material resulting from contact with a chemical. For workwear material, these times vary from five minutes to 48-hours against those recommended in the ASTM D471.
Penetration Penetration is the flow of a chemical through closures, seams and imperfections. Unlike permeation, in which a relatively small amount of chemical is transported to the inside of the workwear, penetration is bulk flow. This includes two pass/fail tests as per ASTM F903. The first pass/fail test should demonstrate no breakthrough indication after five minutes at 0psig. Then 2psig air pressure is applied for 10 minutes, and a second-level observation is made. Failure is determined by a visual indication (usually enhanced by an indicator) of chemicals on the inside of the sample.
Tear Tear is a failure of chemical protective workwear by snagging and tearing and allows direct chemical contact with the skin. This is tested through tear resistance test as per ASTM D624.
Cut Cut is a failure mode when sliced on sharp surfaces, allowing chemicals to penetrate easily. A test method measures cut resistance of materials used in protective workwear and demonstrates its ability to resist the cutting action of a sharp blade under a load. Cut resistance is shown by correlation coefficients, where 0.75 or above is a relatively good result.
Strength Strength is a measure to show the force required to break a sample of workwear material by stretching.
Typically ASTM D412 is used to test strength and obtain data on tensile stress, tensile strength and ultimate elongation.
Leakage Leakage is an integrity measure for gloves and fully encapsulating suits, which can be checked for pinholes and integrity of seams and closures by inflating the product.
Temperature resistance Cold or heat resistant measures are used to evaluate performance under cold and hot conditions. Material behaves differently in various temperatures, hence such conditions should be tested and results included in the product data sheet.
Comfort Comfort in wearing chemical protective workwear is important to obtain the workers’ compliance in using the product properly. There are no standard tests to measure comfort. Subjective user responses are probably the most effective way to rate comfort, and so positive reviews and recommendations from other users could be a good indicator of comfort and fit features of selected workwear.
Work rate, work:rest time ratios, and environmental conditions especially temperature are factors that can contribute to heat stress with full ensembles. The vapour barrier and extra weight of workwear place additional burdens on the body. Another important consideration is that chemical protective workwear can restrict the range of motion or vision, which may interfere with performing the required task. Proper sizes may not be available in all clothing, and the improper size affects comfort.
Additional guidance in selection of chemical protective workwear can be obtained from chemical resistance selection charts in occupational safety and health technical reference manuals.
Use, maintenance and storage Users of chemical protective workwear generally have a false sense of security about the protection provided by such clothing. It is vital to understand that no chemical protective workwear can offer complete protection just by wearing it. Failure incidents always involve human factors and rarely depend on improper equipment alone. If chemical protective workwear is selected, tested and used for its intended purpose, it significantly reduces the probability that it will fail – unless the worker takes a shortcut.
Chemical protective workwear should be used in accordance with the manufacturer’s instructions. Its proper use can only be achieved through adequate instruction, training and supervision. It should be kept in mind that even having the best protective workwear, a single shortcut can impair all its protective features. A good example of this could be failure to clean contaminated workwear during short breaks; workers usually remove the upper half of clothing when leaving the work area for a break. This significantly increases the risk of direct exposure and cross contamination, compromising the integrity of the workwear.
The first and most important step when using chemical protective workwear is a proper visual inspection prior to donning. All testing and product certifications obtained from the manufacturer are for new items and so workwear previously used or exposed to improper storage conditions may have deteriorated its protective barrier. An onsite inspection and check-up is a good idea to identify such flaws. In the case of identification of any flaws impairing the integrity of chemical protective workwear, it should be replaced or returned to an authorised service shop – the user should never attempt to repair damaged workwear.
Other aspects important to safety are the correct maintenance and storage of chemical protective workwear. The employee or the user should ensure that chemical protective workwear is stored in a clean and fully operational condition. Storage arrangements should be such that the equipment is safe from interference and damage, and that it is easily accessible when needed.
Conclusions
The entire process from selecting, using, maintaining and storing the chemical protective workwear requires thorough understanding and experience. It is also recommended to seek advice from a specialist for the intended tasks and use of chemical protective clothing. There are regulations and standards, which also provide extensive requirements on manufacturing, testing and use of chemical protective workwear, however, simple compliance with requirements cannot ensure safety of the workers and relate to a safe workplace. Standards and regulations are there to set minimum requirements, and implementing absolute safety goes above and beyond the regulations to manage the risks at specific site.
Published: 3rd Mar 2015 in Health and Safety Middle East
