20 Safety Practice Questions & Answers

1. 1. A technician will be cutting sheet metal with a power saw and plans to wear a face shield. How should the face shield be used?

   • A.Over safety glasses, which stay on as primary protection.✓ Answer
   • B.Instead of safety glasses, since it covers the whole face.
   • C.Only for cuts that take longer than about a minute.
   • D.Needed only when no safety glasses are available.

   A face shield is secondary protection: it can be lifted, cracked, or allow chips to travel underneath it, so impact-rated safety glasses with side shields stay on beneath the shield. Eye and face protection requirements treat the shield as an addition to primary eye protection, never a substitute for it.

   Source: OSHA eye and face protection requirements; NATE Core knowledge areas, safety — personal safety and work practicesReport a problem with this question

2. 2. Which personal protective equipment is appropriate while brazing refrigerant tubing?

   • A.Dust mask, cotton gloves, no eye protection
   • B.Nitrile gloves, clear glasses, no ventilation
   • C.Rubber insulating gloves and reading glasses
   • D.Shaded eye protection and leather gloves✓ Answer

   Brazing produces intense visible and infrared light, sparks and hot metal, so lenses that filter the glare and leather that resists heat and spatter are required; rubber, nitrile and cotton melt or ignite. Ventilation matters because some silver alloys and fluxes give off toxic fumes, and cadmium-bearing alloys are especially hazardous.

   Source: OSHA welding, cutting and brazing requirements; NATE Core knowledge areas, safety — safe brazing and soldering practicesReport a problem with this question

3. 3. A technician has opened the disconnect for a rooftop unit and applied a lock and tag. What must be done before touching the conductors?

   • A.Confirm that the indoor blower has stopped turning.
   • B.Test the circuit with a meter proved on a live source.✓ Answer
   • C.Brush the conductor with the back of a gloved hand.
   • D.Nothing more; a locked open disconnect proves it dead.

   Disconnects can be mislabeled, a circuit can be fed from a second source, and a meter can fail, so isolation is verified rather than assumed. The live-dead-live method proves the meter on a known live source, shows the target circuit is dead, then re-proves the meter, so a false dead reading from a broken instrument cannot fool the technician.

   Source: OSHA control of hazardous energy (lockout/tagout) rule; NATE Core knowledge areas, safety — electrical safetyReport a problem with this question

4. 4. Three technicians are servicing the same air handler. How should locks be applied at the disconnect?

   • A.The first one to finish removes the lock for a test run.
   • B.A tag alone is enough if the whole crew has been told.
   • C.The lead technician locks it for the whole crew at once.
   • D.Each technician applies and removes only his own lock.✓ Answer

   Group protection depends on every authorized worker holding his own lock, because only that person knows when he is clear of the equipment. If one worker can remove another's lock, the machine can be energized while someone still has hands inside it, and a tag only warns — it does not physically prevent energization.

   Source: OSHA control of hazardous energy (lockout/tagout) rule; NATE Core knowledge areas, safety — electrical safetyReport a problem with this question

5. 5. Power has been removed and locked out at a condensing unit. What must be done before handling the run capacitor?

   • A.Nothing; a capacitor drains the instant power is off.
   • B.Rotate the fan blade by hand to bleed off the charge.
   • C.Discharge it through a resistor across its terminals.✓ Answer
   • D.Short the terminals with a bare screwdriver blade.

   A capacitor stores energy in an electric field and can hold that charge long after the disconnect is open, so releasing stored energy is part of the lockout process rather than an optional step. A resistor bleeds the charge in a controlled way, while a screwdriver short produces a violent arc that can weld the blade, damage the capacitor and injure the technician.

   Source: OSHA control of hazardous energy — release of stored energy; NATE Core knowledge areas, safety — electrical safetyReport a problem with this question

6. 6. A repair could be done with the equipment de-energized, but working it live would save time. What is the correct practice?

   • A.Keep one hand in a pocket while working it live.
   • B.Live work is fine; arc flash starts above 600 volts.
   • C.De-energize, lock out and verify before working.✓ Answer
   • D.Wear leather gloves as insulation and work it live.

   Energized work exposes the technician to both shock and arc flash, and an arc can cause severe burns and blast injury without any contact with a conductor. Because that hazard cannot be eliminated by technique, the rule is to remove the energy whenever the job allows; the one-hand rule and insulated tools reduce risk but never make live work equal to dead work.

   Source: OSHA electrical safety-related work practices; NATE Core knowledge areas, safety — electrical safetyReport a problem with this question

7. 7. Why are gloves and eye protection worn when connecting and disconnecting refrigerant hoses?

   • A.Liquid refrigerant is acidic and burns skin chemically.
   • B.It evaporates before it can ever reach bare skin.
   • C.The only hazard is a temporary rash on the hands.
   • D.Escaping liquid flashes to vapor and can freeze skin.✓ Answer

   Liquid refrigerant boils at a very low temperature at atmospheric pressure, so it pulls heat out of whatever it lands on and produces a frostbite injury; in the eye it can freeze tissue and cause permanent damage. Uncontaminated refrigerant is not an acid, although it becomes corrosive after decomposing in a flame.

   Source: NATE Core knowledge areas, safety — personal safety and work practices; refrigerant safety data sheet first-aid guidanceReport a problem with this question

8. 8. A refrigerant cylinder is transferring slowly and a technician suggests warming it with a torch. Why is this prohibited?

   • A.The heat drives the oil out of the refrigerant.
   • B.Pressure spikes and the cylinder wall can rupture.✓ Answer
   • C.It only scorches paint and makes the label unreadable.
   • D.It wastes fuel gas without raising cylinder pressure.

   Cylinder pressure follows the temperature of the refrigerant inside, and localized flame heating both spikes that pressure and softens the steel where it is applied, which is how cylinders fail explosively. When warming is needed it is done by an approved gentle method such as a warm-water bath, and the cylinder is never allowed to exceed the temperature limit marked on it.

   Source: Compressed gas cylinder handling requirements (OSHA and DOT); NATE Core knowledge areas, safety — safe handling of containersReport a problem with this question

9. 9. Recovery cylinders are filled by weight to a stated maximum and are never filled completely. What is the reason?

   • A.A part-full cylinder is easier for one person to carry.
   • B.Liquid expands with heat and needs a vapor space.✓ Answer
   • C.The space lets air be added to push the refrigerant out.
   • D.The vapor space stops the blend from separating out.

   Liquid refrigerant is nearly incompressible, so once the vapor space is gone a small rise in temperature produces an enormous pressure rise the cylinder was never designed to hold. Filling on a scale, or using a float shutoff, preserves that vapor cushion; judging the fill by feel or sound does not.

   Source: DOT and industry practice for filling refrigerant recovery cylinders; NATE Core knowledge areas, safety — safe handling of containersReport a problem with this question

10. 10. What is the purpose of a pressure relief device on a refrigerant vessel?

    • A.To keep the charge accurate as ambient changes.
    • B.To relieve pressure before the vessel can rupture.✓ Answer
    • C.To protect the compressor windings from overheating.
    • D.To vent refrigerant to keep head pressure low.

    A relief device is a last-resort mechanical safeguard: a vessel that is overheated, overfilled or blocked in will build pressure past its design strength and fail violently, and the device sacrifices refrigerant to prevent that. It is never plugged, capped or adjusted, and if one has relieved, the technician finds and corrects the cause instead of simply replacing the device.

    Source: Pressure relief device function on refrigerant vessels; NATE Core knowledge areas, safety — safe handling of containersReport a problem with this question

11. 11. A large refrigerant leak has occurred in a basement mechanical room. What is the primary hazard to a technician entering the room?

    • A.The vapor gives chemical burns to exposed skin.
    • B.The vapor corrodes the lungs at any concentration.
    • C.The vapor rises and gathers up at the ceiling line.
    • D.The vapor settles low and displaces the oxygen.✓ Answer

    Common refrigerant vapors are denser than air, so a leak pools in basements, pits and crawl spaces and pushes the oxygen out; asphyxiation, not toxicity, is what kills. The space is ventilated and the atmosphere tested before entry, and a technician never enters a low area after a large leak on the assumption that he will smell trouble in time.

    Source: OSHA confined space requirements on oxygen-deficient atmospheres; NATE Core knowledge areas, safety — refrigerant in confined spacesReport a problem with this question

12. 12. An occupant reports headache, dizziness and nausea that ease when she leaves the house, and the gas heating equipment has been running. What should the technician do first?

    • A.Reassure her that the heating system is unrelated.
    • B.Open a window and continue the scheduled service.
    • C.Change the filter and check combustion next visit.
    • D.Get everyone outside, shut it down, and call for help.✓ Answer

    Headache, dizziness, nausea and drowsiness that improve away from the building are classic carbon monoxide symptoms, and CO binds to hemoglobin, so the poisoning deepens the longer people stay inside. Getting occupants out and shutting off the source come before any diagnosis; help means emergency services or the gas utility, and the appliance is not returned to service until the cause is found and repaired.

    Source: Carbon monoxide exposure response guidance; NATE Core knowledge areas, safety — personal safety and work practicesReport a problem with this question

13. 13. A technician confirms a cracked heat exchanger in an operating gas furnace. What is the correct action?

    • A.Seal the crack with a high-temperature sealant.
    • B.Raise the blower speed so the leakage is diluted.
    • C.Leave it running until the owner schedules a swap.
    • D.Shut it down, lock and tag it, and tell the owner.✓ Answer

    A crack lets flue gas, including carbon monoxide, pass into the air the blower delivers to the occupied space, which makes it an immediate life-safety defect rather than a comfort or efficiency problem. The correct response is to take the appliance out of service and document the condition; patching a heat exchanger is not an accepted repair.

    Source: Industry practice on heat exchanger failure and appliance shutdown; NATE Core knowledge areas, safety — personal safety and work practicesReport a problem with this question

14. 14. During a service call a technician finds the vent connector on a gas furnace blocked by debris. Why is this treated as an emergency rather than a maintenance item?

    • A.The burner will not light, so no hazard exists.
    • B.The blockage clears itself once draft is established.
    • C.Flue gas spills indoors and releases carbon monoxide.✓ Answer
    • D.It only lowers efficiency and can wait a few weeks.

    The vent is the only path for flue gas to leave the building, so when it is obstructed the products of combustion spill at the draft hood or vestibule and accumulate indoors. The appliance is shut off until the vent is cleared and proper draft is verified, because incomplete combustion in a spilling appliance drives carbon monoxide sharply higher.

    Source: Venting and combustion spillage principles; NATE Core knowledge areas, safety — personal safety and work practicesReport a problem with this question

15. 15. A technician must work from a ladder near overhead energized conductors. Which ladder is appropriate?

    • A.Any ladder, as long as the job is finished quickly.
    • B.An aluminum ladder with rubber feet to insulate it.
    • C.An aluminum ladder used with leather work gloves.
    • D.A fiberglass or wood ladder, which will not conduct.✓ Answer

    Aluminum is an excellent conductor, so contact between the ladder and an energized conductor puts the technician in the circuit, while nonconductive side rails remove that path. Rubber feet and gloves do not make an aluminum ladder safe, and ladders are kept well clear of overhead lines regardless of material.

    Source: OSHA ladder requirements for construction work; NATE Core knowledge areas, safety — personal safety and work practicesReport a problem with this question

16. 16. What is the correct way to lift a heavy compressor crate from the floor?

    • A.Bend at the waist with straight legs and use the back.
    • B.Squat with a straight back and lift with the legs.✓ Answer
    • C.Lift and turn at the same time to save a step.
    • D.Hold the load away from the body to see the path.

    Keeping the load close shortens the lever arm acting on the spine, and the leg muscles are far stronger than the muscles supporting the lower back, so the squat-and-lift technique lowers the compressive force on the discs. Twisting under load is a common cause of injury, and no technique makes safe a load that is simply too heavy for one person.

    Source: OSHA guidance on manual material handling; NATE Core knowledge areas, safety — personal safety and work practicesReport a problem with this question

17. 17. The thermostat is satisfied and the condenser fan is not turning. A technician wants to reach into the unit to check the fan blade. What should he do?

    • A.Open the disconnect, lock and tag it, and verify.✓ Answer
    • B.Switch the thermostat off to prevent any restart.
    • C.Hold the fan blade with a gloved hand to check it.
    • D.Go ahead; a fan that is stopped cannot start up.

    Condenser fans and blowers are started by controls other than the thermostat — head-pressure controls, defrost boards, time delays and crankcase circuits — so an idle machine is not a de-energized machine. Only opening and locking the disconnect and then proving the circuit dead removes the possibility of an automatic restart with a hand inside the unit.

    Source: OSHA control of hazardous energy (lockout/tagout) rule; NATE Core knowledge areas, safety — personal safety around moving machineryReport a problem with this question

18. 18. Before brazing a line set inside a finished building, what does safe hot-work practice require?

    • A.Clear combustibles, stage an extinguisher, fire watch.✓ Answer
    • B.Switch the building smoke detectors off while working.
    • C.Wet the drywall and leave once the joint is finished.
    • D.Nothing special; the brazing flame is fairly small.

    Brazing heat conducts along the tubing and throws sparks and hot flux, and insulation, framing and stored materials can smolder out of sight and flare up after the torch is off, which is why the fire watch continues past the end of the job. Combustibles are removed or covered with a fire-resistant shield, and the extinguisher is staged where it can be reached without leaving the work.

    Source: OSHA welding, cutting and brazing fire prevention requirements; NATE Core knowledge areas, safety — safe brazing and soldering practicesReport a problem with this question

19. 19. A technician is about to use an unfamiliar coil cleaning chemical. What is the correct step regarding the safety data sheet?

    • A.Use the product first; read the sheet only if hurt.
    • B.Use last year's sheet for a similar coil cleaner.
    • C.Read the current sheet for that product before use.✓ Answer
    • D.Ask the supervisor for permission to see the sheet.

    The safety data sheet — the document formerly called the MSDS — lists the hazards, the protective equipment, safe handling and storage, and the first-aid response for that specific formulation, and formulations change, so the sheet that applies is the current one for the product in hand. Under the hazard communication rule the employer must keep these sheets readily accessible to employees on every shift without their having to ask permission.

    Source: OSHA hazard communication rule — safety data sheets; NATE Core knowledge areas, safety — understanding hazmatReport a problem with this question

20. 20. A technician must service an air handler in an unfinished attic. Which practice is correct?

    • A.Walk on the joists or on planking, and carry a light.✓ Answer
    • B.Skip water and breaks to finish before it gets hot.
    • C.Work by the light coming through the access hatch.
    • D.Step on the ceiling drywall between the joists.

    Ceiling drywall carries no live load, so a foot placed between the members goes through the ceiling and drops the technician to the floor below; the structural members and planking laid across them are the only safe walking surfaces. Attics also bring heat stress, poor lighting, exposed wiring and protruding fasteners, so lighting, hydration and rest breaks are part of working there safely, and truss members are never cut to make room.

    Source: NATE Core knowledge areas, safety — personal safety and work practices; NATE Core knowledge areas, basic construction — ceilings and trussesReport a problem with this question

Practice questions based on the published NATE knowledge areas and standard HVACR theory and service practice. NATE is a mark of North American Technician Excellence; this site is not affiliated with or endorsed by NATE. NATE certification is not a licence — HVAC licensing is set by your state and locality. Confirm current exam requirements with NATE and current code requirements with the authority having jurisdiction. About NATE certification →