Frequently Asked Questions:

What is an arc flash?
An arc flash is a phenomenon where an electric current leaves its intended path and travels through the air from one conductor to another, or to ground.  Because air has such a low impedance, the current releases massive amounts of heat energy (~35,000 ºF) in a violent explosion, causing more than 2,000 burn injuries per year including some fatalities.

What causes an arc flash?
Several factors including accidental touching, dust, dropped tools, material failure, condensation, corrosion, or faulty installation can lead to an arc flash event.

How can an arc flash hurt me?
The typical results from an arc flash include burns (non FR clothing can burn onto skin), fire (could spread rapidly through building), flying objects (often molten metal), blast pressure (upwards of 2,000 psi), sound blast (can reach 140 dB – loud as a gun), and extreme heat (upwards of 35,000 degrees F).

How is arc flash heat energy measured?
Arc flash heat energy is measured in Joules/cm2 or Calories/cm2.  One calorie is equivalent to the energy required to raise one gram of water one degree Celsius at one atmosphere. The onset of second-degree burns may occur from 1.2 calories/cm2.  One calorie/cm2 is roughly equal to holding your finger over the tip of a flame from a cigarette lighter for one second.

What are approach/protection boundaries?
Approach boundaries, as developed by the National Fire Protection Agency (NFPA), are regions surrounding energized equipment that correspond to varying levels of danger if an arc flash event were to occur.  These boundaries are as follows:
Flash Protection Boundary:  The flash boundary is the farthest established boundary from the energy source.  If an arc flash occurred, this boundary is where an employee would be exposed to a curable second degree burn (1.2 Calories/cm2).
Limited Approach Boundary: An approach limit at a distance from an exposed live part where a shock hazard exists. 
Restricted approach Boundary: An approach limit at a distance from an exposed live part which there is an increased risk of shock.
Prohibited Approach Boundary: A distance from an exposed part which is considered the same as making contact with the live part.

 

 

 

 

 

 

 


What PPE is needed to protect myself?
Arc Rated Safety offers a wide variety of personal protective equipment (PPE) to ensure the safety of all customers.
Head: Non-conductive hard hats offer protection from electrical shocks and physical impacts.
Eyes & Face: Safety glasses, hoods, and face shields offer protection from electric arcs, flashes, and flying debris.
Body: Flame resistant shirts, pants, coats, coveralls, and full suits offer protection from extreme heat and burns.
Hands: Insulating gloves and leather protectors offer protection from electrical shocks, cuts, and punctures.
Feet: Dielectric overboots offer protection from electrical shocks around high-voltage equipment.
Equipment: Insulated tools, flashlights, and grounding switchboard mats offer protection from electrical shocks.

 

Are there specific government regulations regarding arc flashes and FR clothing?
OSHA 1910.269 – states “the employer shall ensure that each employee who is exposed to the hazards of flames or electric arc does not wear clothing that, when exposed to flames or electric arc, could increase the extent of the injury that would be sustained by the employee.” This law holds the employer responsible for ensuring that each employee exposed to electric arc flash is protected with the proper apparel, which has been interpreted by most utilities to mean FR clothing, although it is not specifically required in OSHA 1910.269.

What are the guidelines within NFPA 70E on how to assess the arc flash hazard and determine adequate protection for workers?
NFPA 70E cites three methods for assessing a flash hazard:
1) Conduct a flash hazard analysis.  For companies with hundreds or even thousands of employees and a broad variety of work activities taking place around “momentary electric arc and…thermal hazards” every day, this could be an unwieldy task.
2) Use Table 130.7(C)(9)(a) from NFPA 70E to determine the hazard risk category for a specific task.  This table includes a comprehensive list of the most commonly encountered tasks and the associated risk category–and the required protection–for each.
3) Use Annex H from NFPA 70E.  It provides a simplified, two category approach to flame resistant apparel.  While the table and annex provide useful guidelines, remember that the approach recommended is to perform a flash hazard analysis.