Arc flash incidents pose significant risks, with the potential for sudden and intense releases of energy. The various arc flash hazard categories provide a structured framework for assessing the potential severity of such events. These categories, often expressed in terms of cal/cm² (calories per square centimetre), help quantify the thermal energy exposure at specific working distances from the arc flash source.
What is cal/cm?
In the realm of electrical safety, cal/cm, or calories per square centimetre, is a unit used to quantify incident energy. Incident energy is a critical parameter in assessing the potential harm caused by an arc flash event. An arc flash is a sudden release of energy caused by an electrical fault, such as a short circuit or equipment failure. This release of energy produces intense heat, light, and pressure waves, posing a significant hazard to personnel and equipment.
The incident energy is measured in cal/cm² and represents the thermal energy exposure received at a specific distance from the arc flash source. It provides a way to evaluate the severity of an arc flash event and helps determine the appropriate personal protective equipment (PPE) required for workers in the vicinity.
Commonly in the industry when requesting Arc Flash Clothing of PPE, people would refer to them needing a 8cal Poloshirt or 12 cal jacket for example. This is because they are aware of their incident energy and know what class of protection they need.
Arc flash clothing, such as flame-resistant shirts, trousers/pants, jackets, and face shields, is specifically designed to safeguard workers from the thermal dangers of an arc flash. The selection of this protective clothing depends on the calculated incident energy at a designated working distance from a potential arc flash.
The arc rating of the clothing, expressed in cal/cm², is a critical factor in determining its effectiveness. This rating signifies the garment's capability to insulate the wearer from the heat produced during an arc flash event. It directly aligns with the incident energy measurement, ensuring that the protective gear chosen provides an appropriate level of defence against the thermal hazards associated with arc flash incidents.
Understanding HRC 1 (Hazard Risk Category 1)
Caloric Rating: Minimum Arc Rating 4 cal/cm2
HRC 1 is indicative of a low level of arc flash hazard. For this category, the minimum PPE includes flame-resistant clothing, safety glasses, and hearing protection. The goal is to provide basic protection against potential arc flash incidents.
Understanding HRC 2 (Hazard Risk Category 2)
Caloric Rating: Minimum Arc Rating 8 cal/cm2
Moving up the hazard risk scale, HRC 2 requires more robust protection. This typically involves flame-resistant clothing, safety glasses, hearing protection, and, in some cases, face shields. The emphasis is on preventing serious injuries in the event of an arc flash.
We recommend: Arc & Flame Resistant Clothing, Arc Rated Gloves, Arc Face Shield and Safety Glasses,
Understanding HRC 3 (Hazard Risk Category 3)
Caloric Rating: Minimum Arc Rating 25 cal/cm2
HRC 3 signifies a higher level of arc flash hazard. In addition to flame-resistant clothing, safety glasses, hearing protection, and face shields, this category may require the use of arc-rated gloves and other specialised equipment. The aim is to provide comprehensive protection against more severe arc flash incidents.
We recommend: Arc & Flame Resistant Clothing, Arc Rated Gloves, Arc Face Shield , Safety Glasses, Arc Balaclava, FR Base Layers
Understanding HRC 4 (Hazard Risk Category 4)
Caloric Rating: Minimum Arc Rating 40 cal/cm2
HRC 4 demands the highest level of protection, including heavy-duty flame-resistant clothing, arc-rated gloves, face shields, and other specialised PPE. This category is reserved for extreme arc flash hazards.
We recommend: Arc & Flame Resistant Clothing, Arc Rated Gloves, Arc Face Shield, Arc Hood, Safety Glasses, Arc Balaclava, FR Base Layers. (Switching Suits can be utilised, alternatively layering up Arc & Flame Clothing would be much more lightweight and breathable.
Book a complimentary consultation with one of our technical consultants at sales@skanwear.com. Our experts are here to assist you in finding the precise equipment tailored to your needs.
If you already know your incident energy and are looking for a quick solution, explore our product collection pages. Easily filter by Class, Category, and Cal Rating to streamline your search and find the safety gear for your requirements.
