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What does “Hazardous” mean for Electrical Safety?

Electricity can be hazardous to human health and safety in three primary ways: shock, arc flash and arc blast. There are also thermal hazards that can be quite serious. OSHA and NFPA 70E define a simple hazard threshold of 50 VAC. At Berkeley Lab (and across the DOE Laboratory Complex), we are often exposed to a variety of complex electrical hazards. For this reason, Berkeley Lab has adopted the following hazard thresholds. For a complete description and breakdown of the DOE Electrical Hazard Classification System, see Sections 2 & 3 of the LBNL Electrical Safety Manual (ESM).

If a circuit is powered from a source that is rated above the threshold, then it is considered hazardous. Shock and arc flash hazards trigger QEW requirements, while thermal hazards alone do not.


Shock Hazard Thresholds

Source Includes Thresholds
AC 50-60 Hz nominal ≥ 50 V and ≥ 5 mA
DC All ≥ 100 V and ≥ 40 mA
Capacitors All ≥ 100 V and ≥ 10 J
Batteries Lead-Acid and Lithium Ion ≥ 100 V
Sub-RF 1 Hz to 3 kHz (excluding 50-60 Hz nominal) ≥ 50 V and ≥ 5 mA
RF 3 kHz to 100 MHz A function of frequency

From Table 2.2.13 in the ESM


Arc Flash/Blast Hazard Thresholds

Source

Includes Thresholds
AC power 50-60 Hz nominal <250 V and the transformer supplying the circuit is rated >125 kVA

<250 V and the circuit is supplied by more than one transformer

≥ 250 V

Sub-RF 1 Hz to 3 kHz (excluding 50-60 Hz nominal) ≥ 250 V and ≥ 500 A
DC All ≥ 100 V and ≥ 500 A
Capacitors All ≥ 100 V and ≥ 10 kJ
Batteries All ≥ 100 V and ≥ 500 A
RF NA NA

From Table 2.3.3 in the ESM


Thermal Hazard Thresholds

Source Includes Thresholds
Sub-RF 1 Hz to 3 kHz (excluding 50-60 Hz nominal) <50 V and >1000 W
DC All >100 V and >1000 W
Capacitors All <100 V and >100 J
Batteries All <100 V and >1000 W
RF NA NA

From Table 2.3.5 in the ESM