General safety

A field technician does not only fix equipment; you manage hazards while you work. The same systems that move heat store energy in forms that can hurt you if you treat them casually.

This lesson covers the mindset and general practices you will see again in shop and field:

1. Pressurized vessels and piping
2. Electrical energy (lockout, live testing, tools)
3. Heat (torches, hot lines) and cold (walk-ins, liquid refrigerant)
4. Rotating mechanical equipment
5. Refrigerant in the air you breathe
6. Chemicals and cleaning products
7. PPE and professional attitude

A refrigerant cylinder is not “a big can.” Pressure acts on every square inch inside. A large cylinder can hold enormous total force even when the psig reading looks manageable if you misunderstand it.

Field rules:

• Keep valve caps on when required; never drag cylinders without protection.
• Heavy cylinders: chain to an approved cart—not loose in a hot truck bed.
• Store and transport upright so the relief device sees vapor space, not liquid.
• Never heat a cylinder with a torch to raise charging pressure. Warm water not above ~90°F is the approved approach when you need more delivery pressure.
• Wear side-shield glasses and gloves when connecting manifolds or transferring liquid: liquid boils instantly at atmospheric pressure and causes instant frostbite.
• On a large release: move away, find a valve to shut—do not block escaping refrigerant with your hands.

Nitrogen and oxygen service at much higher pressures. Same discipline: cap, chain, cart. Nitrogen for testing always through a regulator, with downstream relief so you do not burst the weakest point (sometimes the compressor shell).

Oxygen: keep lines and regulators oil-free. Never use oxygen to pressurize oily circuits—it can explode fittings or the system.

Current as small as 0.015 A (15 mA) through the body can be fatal. Shock causes burns and heart rhythm problems.

Before touching conductors:

1. De-energize when possible.
2. Lock out / tag out the disconnect; you keep the only key.
3. Test with a known-good meter—not “it looks off.”
4. Treat capacitors and controls as live until proven otherwise.

Use three-prong grounded tools on corded drills unless double-insulated. The green equipment ground on a drill is not optional decoration.

Ladders: use non-conductive (fiberglass or wood) types for electrical work. A non-conductive ladder protects you from grounded shock but not between two live conductors. Extend 3 ft above the landing; base about ¼ of working length from the wall; level, stable feet. Never climb the back braces of a stepladder unless they are real steps. On steep roofs: harness, tie-off, work in pairs. Use a cylinder carrying strap so both hands stay on the ladder.

Torches concentrate heat for soldering and brazing. Restaurants, attics, and cabinets put combustibles near your work.

Before any open flame:

• Know where the fire extinguisher is and how to use it before you need it.
• Keep one on the service truck.
• Use a heat shield on finished surfaces, wires, and cabinet linings.
• Open Schrader ports or service valves before heating sealed tubing—trapped pressure will blow through molten filler and leak.
• In confined spaces: ventilate, keep your face below rising toxic fumes from heated refrigerant.

Extinguisher types matter: A (trash/wood), B (liquids), C (energized electrical). Many service trucks carry dry chemical ABC units rated for all three—using the wrong type can spread the fire.

Liquid refrigerant on skin or in eyes causes instant freeze injury. Long exposure in walk-ins causes frostbite. Step from 95°F ambient into a 0°F freezer prepared—with coat and gloves.

Hot attics and heat waves: watch for red face, dizziness, stopped sweating. Get the person cool; call for help if needed. Wind chill matters outdoors; waterproof boots help with cold and wet but are not your primary electrical protection.

Rotating equipment: no loose sleeves, ties, or jewelry near belts and couplings. Stand to the side when starting an open drive. Never grab a belt to stop a coasting fan—momentum can pull your hand under the belt. Tighten coupling hardware; a thrown nut is a lethal projectile. At the grinder: face shield, correct stone for the metal, tool rest about 1/16 in. from the wheel, never exceed stone rpm rating.

Lift with your legs, back straight; use a back brace when appropriate. Do not solo-lift condensing units—use dolly, lift gate, pry bar, lever truck, or rigging. On roofs and floors: plywood path or short pipe rollers under flat-bottom equipment.

Fresh refrigerant vapor and many other gases are heavier than air. They displace oxygen in low, closed spaces. Symptoms: dizziness, numb lips. Ventilate before you start—fans for cross-ventilation at floor level. Equipment rooms may need refrigerant-specific detectors with alarms and posted warnings. Heated refrigerant (torch near a leak) produces strong, toxic fumes—keep head low and air moving.

Read labels and SDS before using coil cleaners or water-treatment chemicals. Know first aid for eyes before an accident, not after. Motor burnout produces acidic oil and refrigerant—keep distance if a line may rupture. Know where eyewash and emergency call stations are posted.

You are brazing a drier in a restaurant reach-in. Upholstered seating, grease, and paper goods are nearby. The apprentice starts heating before you shield the wiring inside the cabinet.

You stop work. Fire extinguisher verified within arm’s reach. Non-combustible shield in place. Schrader on the process stub is open. Small nitrogen purge (~1–2 psig) flowing so scale does not enter the circuit. Only then does the torch light.

Ten minutes later a customer asks why you “wasted time.” You explain: the cost of one cabinet fire or one acid trip to the ER exceeds every minute of prep.