Chemical protective clothing

February 27, 2002
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Any conscientious employer who cares for its employees wants the best for them. And, certainly, when it comes to safety and personal protection, particularly when working with chemicals or hazardous materials, most employers want their workers to be well protected. In fact, by adequately protecting their employees, they're in essence protecting themselves.

However, is there a point that an employer can go overboard in providing personal protection for its employees? Is there such a thing as too much protection? Are employers using more protection than needed for the sake of convenience or because there's a lack of understanding? And could this, in turn, even be a detriment to the worker?

"Companies could be asking for more protection than they really need," suggests Todd R. Carroll, chairman of both the International Safety Equipment Association (ISEA) protective clothing committee and the American Society for Testing and Materials (ASTM) protective clothing subcommittee F23.30. "On a scale of one to ten, people are going for ten when they may only need a six."

Optimum ensemble

Employers should try to seek the "optimum ensemble" for the primary hazard involved, says Carroll. That is, they need to match the personal protective equipment (PPE) performance to the actual exposure scenario. This may require companies to reassess their PPE programs.

With costs and downsizing the issues that they are in today's business climate, companies may want to take a fresh look at their PPE programs. "They should be asking, 'Where can I downgrade and still get optimum protection?'," says Carroll. This approach may allow employers to consider lower-cost, lighter-weight, less-complex items that might help reduce expenses and actually increase worker protection.

In order to achieve this "optimum ensemble," employers need to know how much protection is needed in a given situation and use the appropriate PPE for that situation. There are several aspects of protective clothing that employers can evaluate to try and streamline their programs.

Breakthrough time

ASTM F739 is the standard test for permeation. It measures the resistance of protective clothing materials to permeation by liquid or gaseous chemicals under the condition of continuous contact. The test determines both the breakthrough time and steady-state permeation rate of chemicals through a sample of the protective barrier.

All chemicals will eventually permeate protective clothing. Breakthrough, or permeation, resistance is related to the concentration and temperature of the challenge chemical, environmental temperature and thickness of the barrier material. Therefore, higher temperatures can result in faster breakthrough. Similarly, lower temperatures can lead to longer breakthrough for certain chemical/material combinations.

The ASTM method establishes the time to breakthrough under conditions of continuous liquid or gaseous contact. The default breakthrough time is 480 minutes (eight hours). According to Carroll, a lot of companies choose clothing materials that offer the eight hours of breakthrough time - which represents a worst-case scenario - when the exposure situation may only require, say, four hours. By properly assessing the resistance of protective clothing materials to permeation, employers can effectively downgrade and still get optimum protection.

Carroll adds that companies can further streamline their protective clothing program by examining ASTM F1383. This test method measures the resistance of protective clothing materials to permeation by liquid or gaseous chemicals under the condition of intermittent splash, not continuous, contact. Why use protection designed for continuous contact with chemicals when the exposure will be a short-duration repeated splash?

Specific hazards

When it comes to hazmat, Carroll says good training is the key. Companies shouldn't automatically assume that the highest level of protective suit is needed. Again, a little research on the part of the employer might result in a downgrade from a Level A protective suit to Level B. This may not only save the company money but also offer the employee such benefits as less equipment to carry around and less chance of heat stress.

PPE should be selected based on the specific hazards present in a given situation. EPA identifies four levels of chemical protective ensembles for responding to chemical spills:

  • Level A protection is used when contaminants are present that require the highest possible degree of both respiratory and skin protection. This ensemble includes the use of an atmosphere supplying respirator such as a self-contained breathing apparatus (SCBA) and a totally encapsulating chemical protective (TECP) suit.

  • Level B is used when contaminants are present that require the same degree of respiratory protection as Level A, but a lesser degree of skin protection such as a splash suit that is not totally encapsulating or gas tight.

  • Level C involves the same degree of skin protection as Level B, but a lesser degree of respiratory protection, which includes air purifying respirators.

  • Level D provides protection against only normal workplace hazards and is not designed to protect against chemical hazards. Equipment may include safety glasses, hard hats, steel-toe boots and leather work gloves.

    Difference in seams

    Another area where employers can maximize their protective clothing ensemble for workers dealing with chemicals, says Carroll, is in seam construction. There are various types of seam construction, and the highest levels are not always needed. Again, it boils down to knowing what the primary hazard is and the exposure duration.

  • Serged seam. This traditional sewn seam is the most economical and cost-effective seam. It is appropriate for low-level exposures, but not suitable for skin-absorbable or skin-toxic chemicals. A serged seam joins two pieces of material with a thread stitch that interlocks. It is typically used on limited-use clothing where dry particulates, non-toxic dirts, dusts and a low concentration of residual contamination are involved.

  • Bound seam. The next level up, this is a serged seam with material folded over the edge and sewn on for a higher degree of protection against liquids and dry particulates. The seam is chain stitched through all of the layers for a clean finished edge.

  • Ultra-sonic seam. Offering yet a higher level of protection, this is a seam without thread - no holes are sewn. Used widely in the medical field and to a lesser degree in the industrial arena, this seam can be liquid-proof and is good for higher splash exposure.

  • Heat-sealed seam. The highest performing and highest cost seam, this seam is sewn and then hermetically sealed with a thermally welded seam tape. The impervious seal provides a liquid-proof seam and should be used when working with a high concentration chemical. Heat-sealed seams are well suited for Level A and B chemical protective clothing.

    No compromise

    Of course, no one is suggesting that anyone compromise the safety of workers. But rather, employers should know what's needed in a given situation and use the appropriate level of PPE based on a well documented hazard analysis. It, therefore, becomes crucial that hazardous situations be properly assessed prior to entry.

    In order for companies to get the biggest bang for their buck, protective clothing must be properly selected and fitted, and workers must be trained in its use, application and maintenance. Selecting the right clothing calls for skill and know-how - knowledge of the workplace and understanding of the potential hazards.

    Since virtually no workplace is hazard-free, protective clothing and PPE will always be an essential component of any occupational safety and health program. Providing the "optimum ensemble" for your workers can keep costs down while giving them protection and comfort.

    SIDEBAR: Purchasing extras

    Just like buying a new car, there are lots of extras that you can purchase when investing in protective clothing, however they come with a price. The key is deciding how much use you'll get out of these features and are they worth the added investment.

    1) Superbarrier materials - provide superior protection against a broad range of chemicals;

    2) End-of-service-life indicators - permeation detectors that tell you when the life of the garment is over;

    3) Personal cooling systems - passive and active devices worn underneath or over protective clothing;

    4) Reflectivity clothing - provides enhanced visibility;

    5) Microporous fabrics - give protective coveralls cost-effective protection against liquids.

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