When it comes to PPE, size matters
One of the more underestimated contributions to the protective qualities of PPE is the relative fit of each element.
As consumers, all firefighters are used to trying on everyday clothing, gloves, shoes, and other apparel to find the best size. When it comes to sizing, there is no real consistency between the same clothing items from different manufacturers. We might know the starting point as a size we are accustomed to wearing, but the item may or may not fit us in a way that is comfortable or looks good.
In the case of protective clothing, wearing comfort is important and to a much lesser degree appearance also can be a factor. Yet, the relative fit is quite important to not only the functional performance of the clothing but also to your overall protection, which in turn directly affects your health and safety.
The adage "it fits like a glove" typically means the apparel perfectly conforms to your body. For firefighter protective clothing, such a fit can be counterproductive and actually negate the performance properties of the clothing.
The material used in your protective clothing consists of many layers. Between each layer and between the clothing and your under clothing and skin are more air layers. These air layers play a significant role on how well the clothing insulates against high heat.
The best example of how this works is a two-pane window. These windows have a trapped layer of air between the two glass panes, which significantly reduces heat transfer through the window. In fact, there is more heat-transfer reduction through the air layer than there is across both glass panes combined.
This is because air is a very effective insulator. Heat moves through air much slower than it does a liquid or anything solid. And this is why all firefighter protective clothing incorporates air layers.
Garments are constructed of at least three layers: outer shell, moisture barrier and thermal barrier. There are air layers between the outer shell and moisture barrier, the moisture barrier and the thermal barrier, and the thermal barrier and your skin.
Most thermal barriers are textile material designed to trap or encapsulate air. Other materials can be added to garments to act as reinforcements or padding, which equally contributes to the number of air layers inside clothing.
Helmets include a large air space above the head — between the suspension that sits on your head and the shell. When properly deployed, the ear covers create an air space between the sides and back of your head.
Footwear, whether leather or rubber, also has multiple layers of trapped air. But the larger air layers occurs between your foot, sock and the boot itself.
Hoods are generally made of two layers of knit fabric. Knit fabrics are constructed in a fashion that traps an air layer between the two knit layers.
Although gloves include multiple material layers, air layers tend to be thinner to reduce bulk and provide the least impact on hand function. Gloves that conform uniformly to the hand provide less impact on dexterity, grip and tactility, but also lessen the amount the thermal insulation. And since the hands have a large amount of surface area, but relatively small volume, protecting the hands becomes one of the larger challenges.
The things we carry
Air layering also changes with the way you wear the ensemble, the other items you wear or carry, and your orientation and activity. These factors in turn affect fit.
The straps and weight of SCBA pull the clothing against the skin. This creates a different fit, but most importantly reduces the thickness of the air layers between materials and skin.
When you bend a knee or elbow, the materials pull more taut against your skin and reduce the underlying air layers. This is why these portions of the clothing tend to have additional padding and materials.
The same thing is true for the other parts of your clothing ensemble. When you clench your hands, the material is drawn closer to your skin. If held that way for a prolonged time, the propensity for greater levels of heat transfer can occur and result in burns.
Similarly, helmet ear covers or boots that are worn too tight can be affected by how you position your body. The amount of overlap between different items of clothing also changes and affects the essential air layers.
Manufacturers attempt to account for the air layers when they design firefighter protective clothing. No one intends for the gear to fit like a finely tailored suit.
The right fit
Protective clothing that is measured to fit for you will better accommodate your body dimensions and shape, though not everyone has access to this type of tailoring. This is why clothing manufacturers go to great lengths to develop special features and styles that find ways to trap air in all wearing configurations but do not restrict movement or diminish functionality.
These principles also apply to helmets, gloves, boots and hoods. While hoods may be a one-size-fits-all type of product, the design of hoods in providing overall protection, especially the ability of the hood to retain its shape and face opening, are characteristic elements for addressing the issue of proper fitting.
Fit is a dynamic property. Something might feel comfortable and reasonable when standing up, but if it inhibits movement and restricts your range of motion when crawling or duck walking, then the clothing really does not fit. Your clothing has to move with you and maintain the all-important air layers.
Despite the best efforts of manufacturers to provide a range of styles and sizes, it is you and your department who are responsible for ensuring that the clothing fits properly. Your department may provide guidance and experience in this area or it may not. Some of the steps that you can follow include:
- Get professionally fitted for pants and coats. Most manufacturers and their distributors or agents, provide detailed guidance for how clothing should fit. When they come to measure you, it often involves much more than simply taking inseams, chest circumferences, and other standard measurements. Some manufacturers will have different sizes available to try on during the fitting process.
- If you cannot get custom-fitted clothing, be careful how you select your size. Your normal suit size may not correspond to the size of protective clothing you wear. Do not accept clothing without trying it on and testing the range of motions and activity you expect to perform while wearing it. This also applies to fitted clothing — you must ensure that the clothing is fully functional in all wearing orientations and take into account the equipment your will be wearing as well as the other elements of the ensemble.
- Boots that comply with the NFPA standards must come in a full range of men's and women's full and half sizes and in three widths. Fewer sizes of gloves are offered. Remember, tight clothing reduces the air insulation layer. At the same time, clothing that is too loose becomes non-functional.
- If something does not fit properly, or your size changes, raise the issue with your supervisor and be refitted. In a lot of cases, departments have stock clothing or sets in selected sizes. If you do not feel that you have the knowledge to make that judgment, seek help from fellow firefighters or manufacturers that genuinely want to provide you the assistance you need.
Remember, properly fitted turnout clothing is more than just feeling comfortable; it is about functional and as safe as possible.
Jeffrey O. and Grace G. Stull are president and vice president respectively of International Personnel Protection, Inc., which provides expertise on the design, evaluation, selection and use of personnel protective clothing, equipment and related products to end users and manufacturers. They are considered amongst the leading experts in the field of personal protective equipment. Send questions or feedback to Jeff or Grace at Jeffrey.O.Stull@FireRescue1.com. The views of the author do not necessarily reflect those of the sponsor.