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Chemical Protective Suits

Published: 10th Aug 2011

It is crucial that protective suits do what they say on the tin, or workers may be exposed to highly hazardous chemicals, radioactivity or biological agents. Not only is it essential that users select the right type of protective coverall, but the coverall must perform to the standard specified on the label.

Suit categories

Suits are labelled according to the level of protection provided for different types of hazards. Within the EU, six categories of protective suit are identified.

With the exception of Type 5 suits, the level of protection reduces from Type 1 suits, which offer the highest level of protection, to Type 6 suits, which offer the least protection.

Type 6 suits are suitable for tasks where occasional splashes by liquids of relatively low toxicity such as many paints are possible.

In contrast, Types 1 and 2 suits (EN 943-1:2002) are designed for working in highly hostile environments, and are fully sealed incorporating breathing apparatus, or air is supplied by an air line. They are used in highly hazardous industrial environments or by emergency responders.

Types 3 and 4 suits (EN 14605:2005) are made from non-breathable, chemically resistant fabrics and have sealed seams. Type 3 suits are designed to withstand a jet of liquid whereas Type 4 suits are designed to withstand a high pressure spray.

Type 5 suits (EN13982-1:2004) are specifically designed to protect against aerosols and dusts and are ?widely used in the nuclear industry, or for working with pharmaceutical actives or experimental animals. Where protective suits are used in the nuclear industry, specific requirements for “protective clothing against radioactive contamination” apply - (EN 1073-1:1998) for ventilated clothing, and (EN 1073-2:2002) for non-ventilated clothing.

Testing methods

The test methods for determining inward leakage for Type 5 (EN13982-:2004) and (EN 1073-2:2002) suits for the nuclear industry are the same, but the results are used to categorise suits for the nuclear industry into three different classes of protection. Class 1 suits offer the lowest level of protection with a nominal protection factor of greater than 5, meaning that up to 20% of a particulate aerosol may penetrate the suit.

The nominal protection factor is calculated from the mean value of the penetration measured at the knee, waist and chest for all the activities undertaken in the test chamber during the test. In addition, the mean penetration for any one activity such as squats must not exceed 30%.

The level of protection actually offered by a suit in practical use is normally lower than implied by the nominal protection factor. If a worker is wearing a relatively tightly fitting suit and undertakes a task which involves repeated physical movements that put a strain on the suit’s fabric or seams, it is highly likely the actual level of protection offered by the suit will be much lower than implied by the nominal protection factor.

Class 2 suits offer an intermediate level of protection with a nominal protection factor of >50 whereas Class 3 suits offer the highest level of protection with a nominal protection factor of >500.

Type 6 suits (EN13034:2005) are designed to protect against splashes and light sprays. Types 3 to 6 suits would normally be worn with gloves, respirator and protective boots, whereas Types 1 and 2 suits are full body suits incorporating protection for feet, hands and face.

Labelling and quality assurance

The labelling of suits is based on meeting strict criteria in standardised tests. These test protocols are also used to assist suit manufacturers or suppliers in product development and quality control. Regular testing provides manufacturers with reassurance that production lines are operating correctly and suits are made to their strict specifications.

Shortcomings in the manufacturing line can lead to defective seams or fastenings. Similarly redesigns intended to reduce the quantity of material used in suit fabrication may adversely affect suit performance, if suits no longer accommodate the types of movement that users make in the workplace.

Major users may commission tests to provide reassurance that the products that they purchase provide the anticipated level of protection of their workforce. Suit testing for the purposes of product labelling to EN standards must be performed by an appropriately accredited laboratory. These tests are designed to demonstrate that suits provide the expected level of protection. The first stage of testing simply involves establishing that suits are fit for wear in the workplace, while undertaking normal workplace activities.

Details of testing methods

The testing is undertaken using personnel drawn from a panel of test volunteers who are familiar with this type of personal protective equipment. Members of the fire and rescue services are ideal volunteers. The volunteers are asked to undertake a standard series of exercises representative of the types of movement that an individual may make in the workplace, including stretches, bends and squats. These exercises quickly reveal if suits are too tight in the bottom, or short in the arms for a wearer within the specified size range, or whether the suit’s seams or material are defective.

Types 1 and 2 suits are subjected to a test to ensure that they are gas tight and must be regularly re-tested during their lifetime to ensure that they continue to provide adequate protection for wearers.

Types 3-6 suits are tested by measuring performance in a standardised protocol designed to replicate key aspects of the environments for which these suits are designed to protect against. Provided suits pass this first stage of testing, then the volunteer will enter a test booth where the suit’s resistance to penetration is assessed.

Types 3, 4, and 6 suits are tested using a low toxicity aqueous dye and Type 5 suits are tested with a sodium chloride aerosol. It is important that suits are tested using volunteers within the specified size range for the suit, ideally at the top end of the size range, particularly for Types 3, 4 and 6 tests. This ensures that the fabric and seams of suits are put under an appropriate degree of stress during the test protocol. In contrast, during the industrial use of protective suits, most wearers prefer to wear a suit that is a size larger than their true size because of increased comfort.

In testing Types 3, 4 and 6 suits, the effectiveness of the suit is judged by the extent to which the dye penetrates the test suit and stains an underlying absorbent white suit - the dosimeter suit. The volunteer wears the dosimeter suit over a spray resistant suit and the test suit is worn over the dosimeter suit (e.g. a total of three suits over long sleeved undergarments - great in winter but not so good in summer!).

The extent of penetration is established by determining the area of dye picked up on the dosimeter suit. In Type 4 and 6 tests, the volunteer marches on the spot while turning slowly on a turntable. The volunteer is subjected to a high (Type 4) or low (Type 6) pressure spray while the turntable makes one full rotation which takes a minute.

The positioning of the four spray nozzles, pressure of the spray and flow rates are strictly specified in the test standard as is the temperature and surface tension of the test fluid. The nozzles, temperature gauges and tensiometer (used to measure surface tension) must all undergo regular calibration in order to ensure that the test conditions meet the specifications set out in the standards.

In a Type 3 test, the wearer is blasted with a high pressure spray to test the integrity of the suit’s seams and other potential weak points (Figure 1). A series of potential weak spots are identified on the suit and each marked with an ‘X’ using a marker pen. These spots are blasted with a jet of dye at a standardised pressure at a distance of one metre. These selected spots are usually on zips, cross over of seams or joins between integrated equipment such as boots or gloves.

Three test spots are tested for each type of potential weak spot. The correct positioning of the jet relative to the target can be achieved using laser sights. If significant quantities of the dye from the test fluid penetrate the test suit and stain the dosimeter suit, the suit fails and the cause of the problem can be investigated.

The design and finish of fabric joins is of enormous importance in determining suit performance. Dye wicks rapidly along threads and features such as a gathered waist can hugely reduce suit effectiveness. Small quality control issues such as use of a blunt needle in machining seams, or incorrect temperature when heat sealing tape over seams can lead to suits failing in the spray test.

In Type 5 tests, the wearer simply wears the test suit over long sleeved undergarments. Three probes are put into the test suit at the knee, waist and chest. The test wearer enters a chamber where a sodium chloride salt aerosol is present (Figure 3). The concentration and particle size of the aerosol are specified in the test standard. The probes in the suit are linked into a photometer which is used to measure sodium concentrations. The extent to which the salt aerosol penetrates the suit is determined by measuring the sodium concentrations inside the suit and comparing them with those inside the chamber.

During the test, the wearer initially stands still while three sets of measurements are made, then three sets of measurements are made while the wearer walks on a treadmill and a final set of three measurements are made while the wearer undertakes squats.

Suits are mostly likely to leak during the squats because of the extra strain put on the seams and fabric. As with the jet and spray tests, seam finish has an important influence on suit performance as well as the type of fabric used.

Other considerations

The tests used to demonstrate that test suits meet the required standards are rigorous, but may not subject the suits to the same stresses and strains as encountered in real workplaces. The test regime does not allow for events such as suits snagging on nails, or for crawling over a tarmac or concrete surface. The tests are also only of short duration and the impact of standing in front of a high pressure jet of fluids for minutes rather than seconds may not be completely predicted by test results.

During testing suits are often taped along the zip and around the cuffs, ankles and hood, which greatly reduces the potential for penetration. Such measures may not be employed during real life use. Suit users would be advised to check the small print in the information provided with suits to see whether the performance standard relates to tests undertaken with taping in place, as they may wish to adopt similar practice.

Overall, the prescribed testing regime for protective suits is highly rigorous, but wearers must be careful to select the correct type of coverall for their applications and to check the small print. Wearers must also have an ongoing awareness of the status of coveralls during use, particularly if suits become damaged, or there is evidence of leakage.

Emergency contingency

It is widely accepted that in the Hierarchy of Controls for managing workplace hazards, PPE should be considered a last resort, after measures to engineer risks out of the working environment have been taken.

Typical minimum standards may be EN13034 for body protection, EN374 for hand protection, EN149 for?respiratory protection from particulates and EN166 for face/eye protection.

It is, nevertheless, essential that PPE is to a standard appropriate to the properties of the substance or product and the circumstances of handling and use. It is also essential that sites are equipped with facilities for emergency treatment, such as emergency showers or eye wash stations. ?

Author

Alison Searl is Director of Analytical Services at the Institute of Occupational Medicine (IOM), where she has responsibility for the work of the UKAS accredited chemistry and mineralogy laboratory and the PPE testing facilities. The laboratory provides analytical services to support occupational hygiene and environmental monitoring including solvents, other organic chemicals, metals, acids, dust, crystalline silica and asbestos in air, water, soil and other bulk materials.

The PPE facility offers a comprehensive UKAS accredited testing service for determining the inward leakage of Type 3, 4, 5 and 6 protective suits for suit manufacturers, certification bodies and end users.

Alison has been at IOM for 18 years having previously taught geology at the University of Birmingham. She undertakes consultancy in relation to chemical risk management, air pollution and health impact assessment in the workplace and wider environment, particularly in relation to exposure to chemicals, gases and airborne particles.

The Institute of Occupational Medicine (IOM)

The IOM is a major independent centre of scientific excellence in the fields of occupational and environmental health, hygiene and safety. It was founded as a charity in 1969 by the British coal industry in conjunction with the University of Edinburgh, and became fully independent in 1990. The IOM’s mission is to benefit those at work and in the community by providing quality research, consultancy and training in health, hygiene and safety and by maintaining our independent, impartial position as an international centre of excellence.

The IOM has more than 120 staff based in Edinburgh, Chesterfield, London, and Stafford.

It offers a wide range of services including occupational hygiene monitoring, health and safety advice and management, asbestos surveys, management advice on asbestos issues, laboratory analysis, health impact assessment, occupational health services and measurement and advice relating to workplace noise, vibration, indoor air quality and office environment. We provide advice on office design, use of display screen equipment and undertake ventilation surveys including validation of hospital operating theatres. We also offer health and safety consultancy, expert witness and consultancy relating to chemical risk management, ergonomics, nanotechnology and other health and safety issues. Our clients include government, government agencies and industry and include both large corporations and small businesses.

In addition to providing services and consultancy, IOM carries out research into a wide range of health concerns, including occupational lung disease, cardiovascular effects, cancer, musculoskeletal disorders, hearing loss, skin diseases, heat strain and psychological stress. The IOM has particular expertise in measuring and assessing exposure to harmful agents, assessing risk and in identifying health effects and their causes and aims to help clients reduce risks by designing interventions involving physical control systems, changing work procedures or modifying worker behaviour. The IOM also has skills in mathematical modelling and the development of survey and measurement methods.

Much of our research is currently funded by EU and UK government as well as industry associations and individual industrial sponsors. Independence and integrity are integral to the operations of both the IOM and its wholly owned subsidiary, IOM Consulting. For more information log on to www.iom-world.org

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Published: 10th Aug 2011 in Health and Safety Middle East

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