Arc Flash Safety
An arc flash is an electrical explosion that can cause severe burns, blindness, and death. Learn what causes arc flash, how to protect yourself, and the regulations.
What is an Arc Flash?
An arc flash is a rapid release of electrical energy through the air when a short circuit occurs. The arc generates temperatures up to 20,000 degrees C (hotter than the surface of the sun), intense light, a pressure wave (blast), and molten metal droplets. An arc flash can cause fatal burns, blindness, hearing damage, and physical trauma from the blast.
Arc flash can occur when working on energised electrical equipment: accidentally shorting across phases with a tool, dropping a tool onto live busbars, or when insulation fails. The risk is highest in high-current equipment like main switchboards, MCCs, and transformers.
Arc flash is survivable with proper PPE
Arc flash PPE (personal protective equipment) is rated in calories per square centimetre (cal/cm2). The PPE category required depends on the available arc flash energy at the equipment. Wearing the correct PPE can prevent burns even in a severe arc flash. Working without PPE on energised high-energy equipment is a death gamble.
Prevention
- De-energise: The most effective prevention. If the equipment is de-energised and locked out, there is no arc flash risk. Always de-energise if possible.
- Work permit: If work must be done energised, an energised work permit is required. This documents the justification, hazards, and required PPE.
- Arc flash study: An engineering study calculates the available arc flash energy at each piece of equipment. The results determine the PPE category required and are posted on warning labels.
- Warning labels: Equipment that poses an arc flash hazard must be labelled with the arc flash energy level and required PPE category.
- Maintain equipment: Loose connections, deteriorated insulation, and contaminated insulators increase arc flash risk. Regular thermographic surveys and maintenance reduce this risk.
- Use insulated tools: When working near energised parts, use properly rated insulated tools to prevent accidental shorting.
PPE Categories
| Category | Energy Level | Required PPE |
|---|---|---|
| 0 | Below 1.2 cal/cm2 | Long sleeve cotton clothing, safety glasses |
| 1 | 1.2 to 4 cal/cm2 | Arc-rated shirt and pants, face shield, hard hat, gloves |
| 2 | 4 to 8 cal/cm2 | Arc-rated coverall, arc-rated face shield, hood, gloves, hearing protection |
| 3 | 8 to 25 cal/cm2 | Arc-rated coverall and jacket, arc flash hood, insulated gloves |
| 4 | 25 to 40 cal/cm2 | Full arc flash suit with hood, heavy insulated gloves |
| Dangerous | Above 40 cal/cm2 | Do NOT work energised. De-energise the equipment. |
Above 40 cal/cm2: do not work energised
No PPE protects against arc flash energy above 40 cal/cm2. If equipment has this energy level, it must be de-energised before any work. If it cannot be de-energised, the work cannot be done. There is no exception to this rule.
Safe Work Practices
- Always verify the equipment is de-energised before starting work. Test with a verified voltage tester.
- Apply lockout/tagout. Don't just open the switch. Lock it. Test for voltage before touching.
- If energised work is justified (troubleshooting, voltage measurement), wear the PPE specified by the arc flash label.
- Stand to the side when operating switches or breakers, not directly in front. Arc flash ejects energy outward.
- Use the right tools: insulated, properly rated for the voltage.
- Keep the work area clear. Remove anything that could cause a short circuit (dropped tools, metal objects).
- Only qualified, trained personnel should work on energised electrical equipment.
Tip: Schedule an arc flash study for your facility. The study identifies the arc flash energy at each piece of equipment, determines the required PPE, and generates warning labels. This is a legal requirement in many jurisdictions and is essential for the safety of your electricians and technicians. PlantLogica can track the study date and remind you when it needs updating.