Hand Protection: Frequently Asked Questions

Customers' questions address usage, shelf life, and disposal.

BECAUSE hand protection plays such a major role in keeping workers safe, questions often arise concerning gloves and their use, care, and disposal. Below are several questions that are often asked by end users.

How can I determine the shelf life of a specific glove?
Two factors will affect the functional storage life of a glove: the type of material the glove is made from and the conditions under which it is stored. To maximize their useful life, all gloves should be stored in a cool environment, shielded from ozone and ultraviolet (UV) light. The latter is especially important for natural rubber gloves, which are extremely susceptible to degradation from UV light--and even the weak UV from fluorescent lights.

While the U.S. Food and Drug Administration has not established any guidelines for the storage lives of surgical and medical gloves, some manufacturers specify a shelf life of five years for these products. The American Society for Testing and Materials is presently developing a protocol for estimating glove shelf life. After this is established, the FDA may change its policy and compile its own guidelines.

Some manufacturers specify a five-year shelf life for industrial-type gloves made of cotton and synthetic materials, with a three-year storage life for natural rubber gloves. In most cases, these are conservative values, especially for synthetic products designed for multiple uses.

Gloves that have deteriorated during storage will have apparent signs of deterioration. They will tear easily when stressed and will develop a hard surface layer that will crack when stretched. The inside of a powder-free glove without a separate donning layer may change from tough polymer to a layer of "goo." If gloves, however, look normal, stretch without surface cracks, and can be pulled onto the hand without breaking or tearing, they will probably provide the level of protection they were designed to provide.

In the case of sterile gloves of any type, the Association of Operating Room Nurses in its 1999 Standards, Recommended Practices and Guidelines recommends that "packages be considered sterile unless damaged or opened." So if older gloves appear to be usable according to the above guidelines, they can also be considered sterile as long as the packaging is undamaged and unopened.

What causes latex allergies, and what can be done to prevent an allergic reaction to latex?
Latex allergy, which is a Type I Allergy, is caused by allergenic proteins that naturally occur in natural rubber latex. While manufacturers of natural rubber latex products have been successful in reducing the amount of these allergenic proteins in gloves, they have not been able to remove them entirely.

If you know or suspect a worker has a latex allergy, you should consider switching to a synthetic alternative. Various manufacturers offer a full line of synthetic gloves made of nitrile, neoprene, and vinyl (PVC).

Could you please provide safety guidelines for using disposable nitrile gloves in the laboratory?
Please keep in mind that no disposable glove will provide perfect protection. You should still work carefully and avoid contact with any chemicals. You also should clean up any spills or broken glass immediately. If hazardous chemicals are spilled on the gloves, the gloves should be discarded and replaced as soon as possible.

Nitrile gloves are especially well suited for use with aliphatic hydrocarbons. The gloves will not deteriorate when exposed to animal fats, lubricating oils, and similar products. They also will protect against water solutions of highly polar materials such as hydrochloric acid, phosphoric acid, sodium hydroxide, and most salts. These gloves are not appropriate for use with highly concentrated sulfuric and nitric acids, although they will resist these acids if the acids are diluted to no more than 50 percent concentration.

Nitrile gloves, however, are not recommended for use with medium-polar solvents such as trichloroethylene, acetone, ethyl acetate, and other solvents with the same polarity. In some cases, natural rubber latex gloves may be substituted. In other cases, only laminate gloves will be able to provide sufficient chemical resistance. They are also thin enough to provide the dexterity needed to handle typical laboratory equipment.

How do I determine my employees' hand sizes so I know the right size gloves to buy?
Use a dressmaker's cloth tape to measure around the hand, above the thumb and below the fingers. Or you may wrap a strip of paper around the hand, mark the length, and then flatten the paper and use an ordinary ruler to determine the length. The diameter of your hand (rounded to the nearest half-inch) is numerically equal to your nominal glove size. (If you use a metric tape measure, divide the centimeters by 2.5.)

This method of measurement, however, does not account for all possible variations in hand size. For example, some people have long, slim fingers and others have short, stubby fingers. You may find that the most comfortable gloves are designated as one-half or even one full size larger or smaller than the measured hand size.

In the past, many glove manufacturers marked their gloves with letter sizes, such as Extra Small (XS), Small (S), Large (L), etc. These designations had little consistency among manufacturers and sometimes varied from one product line to another. As a result, many global glove manufacturers now use numeric sizes for most of their products (e.g., 7-7.5, 8-8.5, 9, 10, etc.).

What is conductive heat, and what is the best type of hand protection to use to protect workers against this type of heat?
Conductive heat is generated by direct contact with a hot surface, such as placing the hand against the very hot wall of a glass furnace or handling hot metal stampings. The only way to protect workers against this type of heat is to provide one or more layers of insulation. For example, you may want to provide workers with gloves that have felt or quilted fabric or foamed polymer liners. Some terrycloth styles also provide some heat resistance. These materials protect the hands by building up an air space between the skin and the heat source.

Some glove manufacturers do not specify temperature ranges for their insulated gloves. Why is this?
Because applications vary so greatly, it is difficult to designate one particular temperature as the maximum or minimum for hand protection. Many factors must be considered, such as whether the source of heat or cold is a liquid, solid, or gas.

If a solid, is the material that will be handled made of a thermally insulating plastic that will minimize heat transfer to the glove? Or is the material a thermally conducting metal that will maximize the heat transfer? Is the material heavy, and how long will it be held? Will the worker repeat the actions that require him or her to wear an insulated glove? Many glove manufacturers specify useful temperature limits for gloves based on the materials used to manufacture the products (see Table 1). While a glove's applicable temperature range will be restricted by these limits, its true useful temperature range will depend on use factors such as those mentioned above. Other parameters include compressibility of the insulation, coating thickness and type of liner, and coating formulation. PVC, for example, can vary widely in its thermal properties, depending on how it is formulated. The ultimate suitability of any insulated glove must be determined by the end users after proper testing.

Table 1: Appropriate Useful Temperature Limits for Various Polymers*

Polymer, Approximate Low Temperature Limit (ºF)
Continuous Exposure, Intermittent Exposure, Short-term Exposure
Cotton, -50, -75, -100
Kevlar(R), -20, -40, -60
Natural Rubber, -10, -25, -50
Neoprene, -10, -25, -40
Nitrile, -20, -20, -40
Nylon, -20, -40, -60
Polyester, -20, -40, -60
PVC, 0, -10, -50

Polymer, Approximate High Temperature Limit (ºF)
Continuous Exposure, Intermittent Exposure, Short-term Exposure
Cotton, 200, 300, 400
Kevlar, 300, 600, 900
Natural Rubber, 170, 300, 350
Neoprene, 200, 300, 400
Nitrile, 250, 300, 400
Nylon, 150, 175, 200
Polyester, 150, 175, 200
PVC, 150, 175, 200

* These temperatures ranges should be used as a starting point for glove selection, not a final choice criterion.

How should I dispose of used gloves?
The answer to this question depends on their prior use. If the gloves are contaminated with a toxic compound or biomaterial that is covered by disposal regulations, they must be handled in the same manner as the toxic material if the material that is in or on the gloves is above the limit specified in the regulation.

If the gloves are not contaminated or have been properly decontaminated, they may be incinerated or disposed of in a landfill. Because ordinary aerobic or anaerobic decomposition processes in gloves will not form any toxic products, the gloves may be disposed of in an ordinary landfill. However, their breakdown will be very slow--except for cotton and natural rubber products, which are more easily degraded by microbial attack.

A well-designed, properly operated incinerator should be able to completely burn all types of gloves as well as any intermediate decomposition product formed during the incineration process. Of course, the higher the temperature and the longer the exposure time, the more complete the combustion.

This article originally appeared in the September 2004 issue of Occupational Health & Safety.

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