Understanding and using protective hoods

PPE Update

with Jeffrey O. and Grace G. Stull
Sponsored by Globe

Understanding and using protective hoods

By Jeffrey O. and Grace G. Stull

Of all the protective elements worn as part of the firefighter's ensemble, perhaps the least appreciated item is the protective hood. Over the past two decades, hoods have become a standard part of the ensemble.

The hood covers the exposed areas of the body that are not covered by the coat collar, SCBA facepiece or helmet. As such, the hood is considered to be an interface item somewhat like the wristlets of coats which help connect coat sleeves and gloves.

Interface areas are for the critical gaps in the ensemble where burns can readily occur if not properly protected. Therefore, the correct selection and use of the protective hood is essential for completing the envelope of protection in this critical head-neck interface area.

The majority of current hoods in the marketplace are of a sock configuration shaped much like a ski mask, having a face opening that fits over the SCBA facepiece. Hoods have bibs that extend down both sides and the front so that the hood remains tucked in under the collar of the coat.

NFPA 1971

The minimum lengths of the bibs are specified by NFPA 1971, Standard on Protective Ensembles for Structural and Proximity Fire Fighting. These lengths generally require the bibs to extend down a couple of inches below the neck on the front and the back and at a slightly shorter distance on the sides.

However, most hoods have longer bibs to ensure that the bib will stay inside the clothing. Some hoods have very broad hoods with panels that extend a significant distance down the shoulders and front and back. Consequently, there are a variety of different styles that are offered by different manufacturers with different bib configurations.

The hood face opening is elastic and likewise has to have minimum dimensions when evaluated according to NFPA 1971. The face opening must also demonstrate a certain size retention as the hood is repeatedly pulled over and taken off the firefighter's head.

Hoods with poor face opening designs can stretch out and are no longer able to make tight contact with the SCBA facepiece. While most knit materials tend to bounce back to their original dimensions after washing, in some cases the continued donning and doffing of the hood can result in elongated openings, which are ineffective.

Opening dimensions

The test in NFPA 1971 for retention of the face opening dimensions actually accounts for 50 repetitions of putting and taking the hood off of a manikin head.

There are relatively few other design features that are common to hoods. In years past, some manufacturers offered hoods with mesh materials in the area of the ear to facilitate the ability of firefighters to hear. There have also been hoods designed with mesh material at the crown of the hood directly underneath the protective helmet to provide for better air movement at the head.

However, there is some consideration of late that the hood should provide uniform insulation protection over the entire head. This issue is still being debated as the NFPA 1971 standard goes through its current revision process.

These products consist of one or two layers of a knit material. Common material fibers include Nomex, PBI, P84, Basofil, Flame Retardant Rayon (also called Viscose) or Carbon-based and various other flame-resistant fibers.

Some material layers are knit 100 percent of one fiber type while many are blends of two or more fibers. Some manufacturers configure their hoods with two layers of the same knit material, while other manufacturers offer one material layer on the outside and another for the inside against the wearer's skin.

Durability and performance

There are several differences in these materials for the department's or firefighter's consideration. They include the relative wearing comfort of the material, its overall durability, and of course its performance. Comfort and durability are best assessed by experience, particularly in talking with other departments that may be using a particular product.

Some products absorb moisture better than others or may feel better next to the skin. While hoods are considered a commodity-like product, subject to more frequent replacement compared with garments and other element ensembles, there is an expected service life that is mainly based on the anticipated level of use.

Most of the performance properties for hoods are the same evaluations that are applied to garment materials in NFPA 1971. This include flame resistance, heat resistance, thermal shrinkage resistance, burst strength, cleaning shrinkage resistance, seam strength, and thread melting resistance.

Some tests such as the flame resistance, burst strength, and seam strength are performed on small samples. Thermal shrinkage (shrinkage caused by high heat exposure) and cleaning shrinkage (shrinkage that results from laundering) are assessed on complete hoods.

The overall heat insulation effectiveness is determined through thermal protective performance (TPP) testing. In this test, hoods are only required to meet a value of 20, while garments have to offer a minimum value of 35 or higher.

The reason for this difference is because as an interface device, hoods do not have to provide as much protection since some attenuation of the heat is caused by the helmet ear covers, coat collar, and SCBA facepiece. Generally speaking, hoods offering the highest TPP values may be the heaviest or least comfortable; however, some novel materials provide very good insulation at low weights.

Unique designs

There are some unique hood designs which approximate multilayer garments by using normal garment outer shells combined with interior knit materials. Some of these designs have hoods that have a manual adjustment to permit closure around the SCBA facepice. In some rare cases, hoods are designed for integration with one specific type of SCBA.

While protective hoods are available in several designs throughout the industry, they are most often provided in only one size, though there are exceptions. Consequently, each firefighter has to be sure that the hood will comfortably fit and most importantly protect any uncovered area of the face not otherwise shielded by the one of the other ensemble elements.

This is best accomplished by putting the hood on and adjusting it as needed and then taking a look in a mirror. In particular, be sure that the hood is covering the sides of the SCBA facepiece and there are no gaps anywhere else in the face covering.

It is also important that your hood is positioned correctly as an interface element in the overall ensemble. For the hood to provide sufficient protection, the bib sections must be completely tucked underneath the coat with the collar in a raised position.

Ear flaps

The helmet ear flaps must also be fully deployed given that that the hood does not provide the same level of insulation as the rest of the garment. Most users will don their hood over their head with their head outside the face opening before putting on their coat (or right after putting on their coat) and then only deploy the hood when necessary at the fire scene. This practice works well only when the hood has been properly and fully positioned with the other ensemble elements before entering the fireground.

Proper care and maintenance is also critical to the hood. Each manufacturer should provide complete washing instructions. Given the simple design for hoods, the hoods are easily washed and dried for reuse.

Washing and drying procedures must be consistent with the manufacturer’s instructions to ensure long life and minimum protection. Similar practices must be exercised for correctly storing hoods out of sunlight and making sure they are dry before they are stored.

Hoods provide a valuable portion of the protection to the firefighter. In a 1990s study, the Fire Department of New York demonstrated the value of hood protective qualities in a variety of laboratory tests and showed how, together with department exposure statistics, proper hood use made the difference in reducing injuries to the head and faces of firefighters.

We look forward to any comments or questions you might have.

Sponsored by Globe

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.

From PPE101.com