Commonly asked questions and answers regarding Personal Protective Equipment (PPE).
What personal protective equipment (PPE) protects a person from a shock or electrocution?
For shock or electrocution to occur, a worker must experience current flow through his or her body. Insulating materials decrease the amount of current. Generally, rubber products are good insulators in some cases, however, a rubber product might contain a contaminant, be semi-conductive, or intentionally contain a conductive component. Workers should use only insulating products that are assigned a rating by the manufacturer.
Why must conductive apparel such as rings be removed when working on or near live parts?
Conductive apparel provides a mechanism to initiate an arcing fault by creating a short circuit. Conductive apparel may be the low-resistant point of contact that results in an electrocution. Metal components of apparel also absorb and retain thermal energy from an arcing fault. If the metal component is in a worker’s pocket, the protective nature of the flame-resistant PPE is decreased.
What is FR clothing?
Flame-resistant of FR clothing protects the wearer from the thermal effects of an arcing fault. FR clothing should be arc rated. FR clothing used for protection from an arcing fault must be rated for use in an environment influenced by an electrical arc. Such apparel is assigned an arc rating in calories per square centimeter.
Some children’s clothing and some bedding are rated as flame retardant. Generally however, the flame retardant property is the result of treating the fabric with a chemical. The chemical (and flame retardant property) will deteriorate as the product is laundered.
When can I use the table method to determine FR Protective equipment?
Table 130.4(D)(a) and Table 130.4(D)(b) in NFPA 70E 2015 identifies various work tasks, categorized by equipment type. Using these tables is an acceptable method to determine PPE requirements. However, the notes that follow the table describe the conditions under which the table applies.
Why is FR clothing rated in calories per square centimeter?
All current methods of estimating the thermal hazard in electrical equipment determine incident energy in calories per square centimeter. The unit of measure is not important except that it becomes a standard designation. Arc-rated clothing is rated as calories per square centimeter to enable direct comparison of incident energy and the protective nature of the clothing.
What happens if the FR rating of the PPE is less that the exposure?
When a worker is exposed to incident energy that exceeds the rating of his or her protective clothing, an injury might occur. However, the worker’s clothing will not ignite. The under-rated clothing will provide some thermal protection. Although an injury might occur, the arc-rated clothing will mitigate the exposure to some extent.
Will FR clothing protect me from shock of electrocution?
No. Electrical shock or electrocution is the result of electrical currents flowing through a victim’s body. Any time an exposed energized conductor is touched simultaneously with contact with earth, current will flow. To prevent electrical shock, the amount of current must not exceed 0.006 amperes. Only products that are tested to control current flow will do that. FR Clothing is constructed from fabrics that may ne conductive.
Is fit important when wearing FR clothing?
When the surface of the clothing is heated, the thermal energy is conducted through the fabric to the surface underneath. If the fabric is tight on a worker’s skin, the skin could be burned by the energy conducted through the clothing.
A couple of principles can help guide you in seeking the right fit. First, movement should be unimpeded by a garment that is either too loose or too tight. Second, wearing layers may help protect from both flame and conduction. In general, you should choose your clothing based on the risk you are likely to face while doing particular tasks.
When is an arc rated face shield satisfactory?
An arc-rated face shield worn in conjunction with an arc-rated balaclava (head sock) might provide adequate protection from arc flash. The face shield must be rated for both impact and thermal protection. Workers should recognize that the side of the face shield is open and might expose the side and back of the worker’s head to thermal energy.
Why is it important to wear spectacles under a face shield of flash hood?
A face shield or flash hood will protect your eyes from impact just as spectacles would. However, when you remove the face shield of the flash hood, your eyes are exposed just as if the spectacles have been removed. If you forget to put your spectacles back on, the eyes are unprotected for a longer period of time.
What clothing must not be worn when exposed to arc flash exists?
When an arc flash event occurs, the air (and gases that result from the plasma) will reach a temperature of 18,000° F to 20,000°F. Ordinary street clothing made from cotton or cotton blends will ignite at between 600° F and 1,000 °F. If a worker’s clothing ignites, the worker’s skin is exposed to the temperature of the burning clothing for several minutes. The result will be very significant burns. Clothing made from cotton, cotton blends, or any other flammable or meltable fabric must not be worn.
Any part of your body that is close to a potential arcing fault than to the flash protection boundary must be protected. The PPE must have an arc rating at least equal to the estimates incident energy. The overall protective apparel may be assembled from several individual components, such as shirt and pants, provided the overall apparel covers all parts of the body exposed to the hazard. Note that a lab coat might protect the upper section of the person’s body and not protect the lower portion of the body.
What is the danger associated with the thermal hazard?
The most significant result of the thermal hazard is the possibility of igniting a worker’s clothing. Certainly a worker’s unprotected skin is likely to be injured in the exposure. However, when a worker’s clothing ignites, the duration of the exposure will be longer and result in more severe injury.
What is the best PPE practice for workers who may be exposed to arc flash?
The most significant burn injuries occur when a worker’s clothing ignites. In most cases, the duration of an arcing fault is short. Although the temperature of the arc plasma is very high, limiting the duration of the arc flash event limits the duration of the exposure. However, when a worker’s clothing ignites, the worker’s skin is exposed to the burning clothing for several minutes. When exposed to an arc flash event, workers tend to become disoriented and thus may have difficulty removing burning clothing, which further extends the exposure. This normally results in extensive burns.
Any arc-rated FR clothing will not ignite. All workers who are or may be exposed to an arc flash event should avoid clothing constructed from any non-FR fabric. Category 2 rated clothing has a feel that is similar to ordinary work clothing. Workers should wear arc-rated FR clothing that is rated as category 2 protection.