- ISHN GLOBAL
- EHS RESEARCH
As a technical support specialist for a safety supply company, Iâ€™m daily assisting our customers with determining which chemical-resistant gloves are appropriate for a given work application. Sounds simple enoughâ€¦ donâ€™t you just pull out the handy â€œglove selection guideâ€ provided by the glove manufacturer and read off their selection? If only it was that easy.
Since OSHA expects employers to evaluate which personal protective equipment (PPE) to use when working with different chemicals, customers are typically left with two choices in making this determination:
1) Review the Material Safety Data Sheet (MSDS) or;
2) Review with their safety supplier/glove manufacturer (from prepared compatibility charts).
You will probably find that most MSDSs are quite vague in their PPE recommendation, and I would caution you on using this information exclusively without confirmation. Many MSDSs simply state â€œuse a chemical-resistant glove when handling this product.â€ Obviously, this statement is of little value to the customer trying to document which glove their employees should use for a specific work application. While MSDSs are very helpful in identifying percentages of ingredients found in chemical mixtures (laquer thinners or janitorial chemicals, etc.), it still makes sense to review chemical compatibility charts when needing to select a proper glove.
Treat it as an experimentAny time you select a new chemical glove to use for a new or existing work process, you must treat it as an experiment. Put yourself in the mindset that a new glove application in your workplace has never been duplicated before anywhere in the world. While this may seem a little extreme, remember that your employees are using these gloves in a unique manner that other companies do not exactly duplicate (hand manipulation, length of time in chemical, weight of objects being handled, etc.).
While there may be 10,000 other companies using the same chemical and performing a similar task, chemical glove longevity can vary based on a number of factors. Also, if a given chemical is listed as relatively toxic or can be readily absorbed through the skin, your frequency of glove change-out will be affected by these variables. Employees need to be trained on the potential signs of glove incompatibility and wear.
Letâ€™s take a closer look at some of the key factors in glove longevity and in making our selection.
DegradationThis is the reduction in one or more physical properties of a glove material due to contact with a specific chemical. In essence, degradation charts assist employers in determining how quickly a given chemical will â€œeat awayâ€ at the glove material that is protecting your hand. Exposed glove materials may get harder, stiffer and brittle, or they may get softer, weaker and swell to several times their original size (all these factors depend on the chemical and glove material being used). Degradation ratings are not precise and time limits are difficult to judge, but this can be one helpful tool in determining compatibility of a glove material with a certain chemical.
For many years, the selection of chemical gloves was commonly based on degradation data alone, but some chemicals will permeate rapidly through certain materials that have acceptable degradation resistance. This means that workers may be exposed to such chemicals even when they believe theyâ€™re adequately protected.
Permeation and degradation do not always correlate.
PermeationThis is the process by which a chemical moves through a glove material on a molecular level. Molecules of the chemical figuratively â€œsquirmâ€ through the molecules of the glove film and pass through to the other side and begin to contact the skin.
Manufacturers typically test their glove film material by the use of a small swatch which has been completely immersed with a chemical on one side and with a sensor probe on the other side timing exactly when the sensor â€œsniffsâ€ or senses the chemical beginning to break through. This is referred to as â€œPermeation Breakthrough Time.â€
As an example, just because a particular glove has a listed breakthrough time for a specific chemical at 60 minutes, that does not automatically mean the gloves must be thrown out exactly after one hour of use.
First of all, most chemical glove applications are not completely immersed for such a long timeframe.
Second, just because permeation breakthrough occurs at a specific time, this does not mean the chemical is â€œgushingâ€ through the glove (see the definition of â€œpermeation rateâ€).
When chemical resistance testing is done on gloves, all manufacturers perform this testing at 72ËšF (room temperature). In general, for every 17-degree rise in temperature, the breakthrough time is reduced by half, and the permeation rate will double. Many scientists concur that even your skin temperature will affect the validity of these permeation/degradation chemical charts and how they relate to real-world applicability.
Another factor affecting both permeation and degradation is the manufacturersâ€™ individual formula for the ingredients of their gloves. All glove manufacturers use the same names (nitrile, vinyl, neoprene, etc.) to describe their compounds, however, the gloves can perform somewhat differently to various chemicals. So now we have to consider not only the material of the glove, but also which brand we pick for the application.
Permeation rateThis is the average constant rate of permeation that occurs after breakthrough when the chemical is continuous and all forces affecting permeation have reached equilibrium. To put it in more simplistic terms, it means that after permeation takes place, does the chemical leak through the glove very slowly or does it gush through? This actually is important, because you can typically continue to use a glove after permeation breakthrough occurs (for a limited period of time), provided the permeation rate is very slow (and you are not dealing with a very toxic product).
Glove thicknessWhen referring to a glove thickness, you will always see the term â€œmilâ€ being used. A â€œmilâ€ is equal to 1/1,000 of an inch (or .001â€). Glove thickness can only be measured on unsupported gloves (which do not have a fabric liner).
It can be very helpful to know the thickness of unsupported gloves since it gives us a point of comparison for longevity of gloves from a chemical permeation viewpoint. Common sense tells us that a thicker glove will allow a longer permeation breakthrough time and permeation rate. We must realize that glove manufacturers do not list permeation data for every thickness of gloves they distribute.
Cost savingsWhile the ultimate advantage/goal of choosing the correct chemical-resistant glove is the health and well-being of your employees, it is not uncommon for employers to realize potential cost savings of the gloves, as well. Through proper review of the work process and chemicals being handled, less expensive alternatives can be investigated.
Employers sometimes purchase the cheapest gloves available that are inappropriate for the chemical situation, and this can commonly result in chemical dermatitis and frequent glove replacement. This is an example of an experiment gone wrong and this way of thinking will only cause problems. Be prepared that some categories of chemicals require more expensive gloves than you might be used to using, however, there typically are options available for all types of work situations. We need to remember that our hands are our â€œliving glovesâ€ and we must do everything we can to keep that pair clean and healthy throughout our life.
SIDEBAR: Care of glovesEven the most appropriate chemical glove for a given application will wear out quicker if the employees donâ€™t take proper care of them. Providing that it is appropriate to do so, rinsing/cleaning/wiping the gloves off after chemical contact will almost always lengthen the life of the glove. By leaving chemical residue on a glove to simply â€œevaporateâ€ off over time, you are giving the chemical residue a chance to both permeate and degrade the glove material. After repeated exposure to specific chemicals, the glove film allows the chemical to permeate that barrier a little easier each time. Keeping the gloves clean and dry helps maintain a longer life expectancy for that product.
SIDEBAR: Supported vs. unsupported glovesUnsupported gloves can be compared by thickness. Supported gloves start with some form of a liner and are dipped, typically multiple times, into the compound of choice (nitrile, vinyl, butyl, etc.). Here is a comparison of the attributes of each category of glove:
Supported gloves: heat and cold resistance, absorb sweat, liner enhances the strength and durability of the glove (cut, puncture and abrasion resistance).
Unsupported gloves: lower cost, better dexterity/tactile sensitivity, easier to select thickness of gloves based on application.