Page 44 - OHS, March 2021

PPE: PROTECTIVE APPAREL
Understanding some basic terms will help give you confidence in your rainwear.
Remember that the Hydrostatic Pressure Test, also known as the Water Column Test, doesn’t test real life situations, which are more dynamic than static.
According to Gore-Tex, “When a raindrop falls on a garment, the process is dynamic, but this is not simulated in the water column test. Even fabrics with very low water column ratings have turned out to be waterproof under real life conditions. The Swiss Federal Laboratories for Materials Science and Technology (EMPA) analyzed several garments made with fabrics whose water column ratings were below 120 mm and established that the garments remained fully waterproof when rainfall was simulated. These were closely woven fabrics with a water-repellent fabric treatment. Compared with ratings of 10,000 mm or even 20,000 mm, it is hard to believe that these fabrics could be used to produce waterproof garments. Nevertheless, in the retail trade, water column test methods and ratings are the generally accepted way of determining the degree of ‘waterproofness.’”
If you need to buy a lot of rainwear, you should also test the garment in the rain. Most top-tier safety companies will provide free samples to test and try out for industrial applications.
Waterproof, Breathable Gear. Breathable waterproof rainwear not only keeps the rain from touching your skin, but it is also constructed to move your sweat to the outside of the garment, keeping both precipitation and perspiration at bay. If the job requires lots of physical activity in a steady downpour, you will want to specify waterproof breathable rainwear since it usually allows for “moisture vapor transfer,” the efficiency of which determines if you feel comfortable or clammy.
Waterproof/Breathable products are usually constructed using stitched and tape-sealed seams to ensure integrity during inclement weather conditions.
Waterproof, Non-Breathable Gear. Non-breathable waterproof rain gear is great if you are just sitting or standing around outside in the rain. A lot of affordably-priced, general-purpose rain slickers and ponchos fit into this category. In addition to work applications, a lot of people will wear these at outdoor concerts and sporting events when it rains. However, if you become active in this attire, you’ll feel clammy and uncomfortable because the inside of the rainwear will become rather slick from the lack of moisture transfer.
In industrial situations with chemical hazards or hydro- blasting with high water PSI factors, choose rainwear products that are waterproof non-breathable. Features of these garments should be minimal to avoid catching on equipment, which could produce rips and tears, exposing workers to dangerous chemicals.
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When assessing your jobsite for rain hazards this spring, ask these questions:
■ What are the tasks that will be performed in the rain? Are they physically active tasks or inactive tasks?
■ Duration of use—how long will the worker be impacted by the rain?
■ Are there other hazards present, such as chemical splash or risk of electric shock?
■ What rainwear standards are required for this job or appli- cation? (ANSI/ISEA 107-2015, F-1891/F-2733)
■ Does the application require waterproof/breathable or wa- terproof/impermeable?
Understanding Basic Rainwear Terms
What should I choose? Water-resistant, waterproof or water- repellent rainwear?
It is important to understand the differences between water- resistant, waterproof and water-repellent rainwear. This is especially important in spring months because storms and flash floods can create a miserable workday if not properly protected.
Water-resistant. Both “water-resistant” and “waterproof” designate the degree of water penetration.
Water-resistant apparel resists the penetration of water, but not entirely. This is considered the lowest level of water protection. It is breathable and can handle light rainfall and snow flurries for a brief time. However, during extended downpours and slanting sideways rain, your comfort and level of dryness will be compromised. Water-resistant outerwear is not designed to withstand heavy exposure to the elements.
Waterproof and the Hydrostatic Head Test (HH). A waterproof rain jacket is impervious to water, acting as a barrier to keep rain, sleet, wind and snow from penetrating the gear. It offers the highest level of protection from water and can be either breathable or non-breathable.
According to the Hydrostatic Head Test (HH), waterproof fabric should be able to resist a water pressure of about 1,500 mm (lowest) to 40,000mm+ (highest). It is measured as a length— usually in millimeters (mm)—representing the maximum height of a vertical column of water that can be placed on top of the fabric before water begins to seep through the weave. It is often used to measure the waterproofness of outerwear, tents and backpacks. The higher the number, the better the resistance to the rain.
Understanding HH grading numbers will help you make an informed buying decision about the outerwear that is best for your jobsite. See the chart below for easy reference to the HH grading scale.
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If your jobsite experiences...
Choose waterproof outerwear with an HH Grading Scale in millimeters (mm)
LIGHT & INFREQUENT
drizzle or snow dustings
1,500mm to 5,000mm
MODERATE & STEADY
rain or snowstorms
5,000mm to 10,000mm
HEAVY & FREQUENT
rain or snowstorms
10,000mm to 40,000mm+
40 Occupational Health & Safety | MARCH 2021
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