Safety Protocol 001: Plasma Arc Technology — Electrical, Thermal & Radiation Hazards

Protocol ID: U5M1-SAFE-001 Context: Safety procedures for plasma arc cutting operations, addressing the unique hazards of high-temperature ionized gas, high-voltage arc initiation, UV/IR radiation, and metal fume exposure Hazard Level: Very High — Plasma cutting involves temperatures exceeding 30,000°F, high voltage (up to 300V DC), intense UV radiation, and molten metal ejection

Potential Hazards

Electrical Hazards

• Open circuit voltage (OCV): Plasma cutters produce 200-300V DC to initiate the arc — lethal voltage levels. Contact with the torch electrode, workpiece, or water table while the machine is armed can cause electrocution
• High-frequency start circuits: Some plasma cutters use HF (high-frequency) arc starting, which can interfere with pacemakers and cause RF burns
• Ground faults: Improper grounding of the workpiece or work table can create shock hazards through the metal being cut

Thermal Hazards

• Plasma arc temperature: 25,000–45,000°F (14,000–25,000°C) — far exceeding the melting point of any metal cut in a makerspace
• Molten metal and dross ejection: The plasma jet expels molten metal at high velocity below and around the cut
• Workpiece heat: Cut metal remains at 300-800°F for minutes after cutting — handling before cooling causes severe burns
• Fire risk: Sparks and molten metal can travel 20-35 feet and ignite combustible materials

Radiation Hazards

• UV radiation: The plasma arc emits intense ultraviolet radiation (UV-A, UV-B, UV-C) that causes arc eye (photokeratitis) and skin burns — similar to welding arc exposure
• IR radiation: Infrared radiation from the arc and heated metal can cause thermal eye injury with prolonged exposure
• Visible light intensity: The arc is bright enough to cause retinal damage with direct viewing

Respiratory Hazards

• Metal fumes: Cutting steel produces iron oxide fumes. Cutting galvanized steel produces zinc oxide fumes (causes metal fume fever). Cutting stainless steel produces hexavalent chromium (carcinogen)
• Ozone and nitrogen oxides: The plasma arc generates ozone (O₃) and NOx gases — respiratory irritants at low concentrations, toxic at high concentrations
• Particulate matter: Fine metal particles become airborne during cutting

Noise Hazards

• Arc noise: Plasma cutting produces 95-115 dB depending on amperage and material — exceeds hearing damage thresholds

Required Precautions & Procedures

Before Operation

1. Inspect all cables, hoses, and connections for damage — do not operate with frayed or cracked cables
2. Verify the work clamp makes solid metal-to-metal contact with the workpiece
3. Clear all combustible materials within a 35-foot radius of the cutting area (NFPA 51B requirement)
4. Verify fire extinguisher (ABC or CO₂) is within 15 feet
5. Ensure ventilation system or fume extraction is operating — minimum 100 CFM per square foot of cutting table
6. If using a water table, verify water level covers the bottom of the workpiece
7. Never cut in wet conditions or while standing on wet surfaces
8. Verify all personnel in the area are wearing appropriate PPE or are behind welding screens

During Operation

1. Never touch the torch tip, electrode, or workpiece while the machine is armed (power on)
2. Maintain at least 12" clearance between the torch and any body part during cutting
3. Keep the work clamp attached to the workpiece at all times — never cut with a disconnected ground
4. Do not cut containers that have held flammable materials unless they are certified purged and gas-free
5. Do not cut galvanized, painted, or coated metals without proper respiratory protection (minimum P100 with OV cartridge)
6. Monitor for fire — assign a fire watch if cutting near combustible structures

After Operation

1. Allow cut parts to cool for a minimum of 5 minutes before handling — use pliers or tongs for hot parts
2. Mark hot metal with soapstone "HOT" to warn others
3. Turn off the plasma cutter power supply at the main switch
4. Inspect the cutting area for smoldering materials, especially below the cut table
5. Maintain fire watch for 30 minutes after cutting operations cease (OSHA recommendation)

Emergency Response

1. Electrical shock: Do NOT touch the victim if still in contact with the circuit. Disconnect power at the main breaker or use a non-conductive object to separate them. Call 911. Begin CPR if the victim is not breathing
2. Severe burn: Cool with clean running water for 20 minutes minimum. Do NOT apply ice directly. Do NOT remove clothing stuck to the burn. Call 911 for burns covering >10% of body area or affecting face/hands/joints
3. Arc eye (flash burn): Move to a dark room, apply cool wet compresses, do NOT rub eyes. Seek medical attention — symptoms may worsen over 6-12 hours
4. Metal fume fever: Move to fresh air. Symptoms (flu-like: chills, fever, muscle aches) typically appear 4-12 hours after exposure. Seek medical attention. Report the type of metal that was cut
5. Fire: Press E-stop. Use fire extinguisher (aim at base of flames). If fire spreads beyond initial containment, evacuate and call 911
6. Report ALL incidents, including near-misses, to the lab supervisor

PPE Requirements

PPE Item	Specification	Required When
Welding helmet/shade	Shade 8-9 for plasma cutting <40A; Shade 9-12 for 40A+	During all cutting operations
Safety glasses (ANSI Z87.1)	Worn under welding helmet	Always in plasma cutting area
Leather welding jacket or flame-resistant shirt	FR-rated (ASTM F1506)	During all cutting operations
Leather welding gloves	Gauntlet style, minimum 14"	During all cutting and material handling
Leather boots	Steel/composite toe, 8"+ shaft, no laces exposed	Always in cutting area
Hearing protection	NRR 25+ earmuffs or plugs	During all cutting operations
Respirator	P100 with OV cartridge (half-face minimum)	During all cutting, especially coated/galvanized metals
Leather apron	Full-length	When cutting with manual torch (not CNC table)
No synthetic clothing	Polyester/nylon melts into skin	Never wear synthetic fabrics near plasma operations

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Last Updated: 2026-03-19