Arc Flash Jacket for Electrical Professionals. by Emco Group India

What is Arc Flash:

How can such a problem develop? A transient of sufficient magnitude can cause an arc to form between conductors within an instrument or across test leads. Once an arc occurs, the total available fault current can feed the arc and cause an explosion.

The result is an arc flash, which can cause a plasma fireball fueled by the energy in the electrical system. Temperatures can reach about 3,000° C or 5,000° F, instantly burning or melting any non-retardant clothing and causing beyond third-degree  burns. The arc can also cause a sonic and pressure wave capable of spraying a bystander with molten metal inducing further, deeper burns.

Transients are not the only source of arc-flash hazard. A very common misuse of hand-held multimeters can trigger a similar chain of events. If the multimeter user leaves the test leads in the amps input terminals and connects the meter leads across a voltage source, that user has just created a short through the meter. While the voltage terminals have a high impedance, the amps terminals have a very low impedance. This is why a meter's amps circuit must be protected with fuses.

Another common and dangerous misuse of test equipment is measuring ohms or continuity on a live circuit. These measurements should be made only on circuits that are not energized.  Working on live voltage must be only the last resort.

Classification of Cat as Per NFPA-70 E. Regulations:

CAT 0 (NO CAT RATING AS4836)

No cal/cm^2 rating, and is simply flame retardant (FR). It is possible for a garment to be flame

retardant, and not have an Arc Flash cal rating. It is not possible to have a cal rating without being

flame retardant. This is because an Arc Flash cal rating is achieved by exposure to an Arc Flash

test, while an FR garment or fabric is simply exposed to a static flame test. As such, we know

all Arc Flash cal rated garments will pass a FR test as they must be FR to pass the Arc Flash test.

A fabric that passes only a FR static flame test, is by no means guaranteed to pass an Arc Flash CAL

rating test.

CAT 1 (4-7CAL/CMSQ NFPA 70E)

The popularity of Cat 1 clothing for all day work wear is increasing exponentially.

It was seen as a ‘must have’ to have over 8cal/cm^2 for work wear.

This is changing, with more and more companies accepting lower values

(5-7cal/cm2) for their work wear, in order to achieve wearability and breathability

benefits only offered by lighter but lower rated fabrics.