20 Safety Practice Questions & Answers

Every Safety practice question from the NATE HVAC Practice Test, with the correct answer and a short explanation.

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.It is worn over safety glasses, which remain the minimum eye protection.✓ Answer
- B.It replaces safety glasses, since it covers the entire face.
- C.It may be skipped for short cuts that take less than a minute.
- D.It is needed only when safety glasses are unavailable.
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. Which personal protective equipment is appropriate while brazing refrigerant tubing?
- A.A dust mask and cotton work gloves
- B.Nitrile gloves and no eye protection, since the flame is small
- C.Rubber insulating gloves and clear reading glasses
- D.Shaded eye protection and leather gloves, with adequate ventilation✓ 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. 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, proving the meter on a known live source both before and after the test.✓ Answer
- C.Brush the conductor briefly with the back of the hand to feel for a tingle.
- D.Nothing further; an open, locked disconnect proves the circuit is 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. Three technicians are servicing the same air handler. How should locks be applied at the disconnect?
- A.The first technician to finish removes the lock so the unit can be tested.
- B.A tag alone is enough as long as everyone is told the unit is being serviced.
- C.The lead technician applies one lock on behalf of the whole crew.
- D.Each technician applies a personal lock, and each removes only his or her own.✓ 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. 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 removed.
- B.Rotate the fan blade by hand to bleed off the charge.
- C.Discharge it through a resistor placed across its terminals, because it can hold a dangerous charge after power is off.✓ Answer
- D.Short the terminals together 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. A repair could be done with the equipment de-energized, but working it live would save time. What is the correct practice?
- A.Work it live but keep one hand in a pocket, which makes it equivalent to de-energized work.
- B.Live work is equally safe on low-voltage control circuits and on line-voltage circuits.
- C.De-energize, lock out and verify; energized work is justified only when de-energizing is genuinely infeasible, and then with insulated tools and rated protection.✓ Answer
- D.Work it live while wearing leather gloves.
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. Why are gloves and eye protection worn when connecting and disconnecting refrigerant hoses?
- A.Liquid refrigerant is acidic and causes chemical burns on contact.
- B.Liquid refrigerant is harmless because it evaporates before it can reach skin.
- C.The only hazard is a temporary skin rash.
- D.Escaping liquid refrigerant flashes to vapor, absorbs heat instantly and can freeze skin or eye tissue.✓ 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. 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.Direct flame raises internal pressure rapidly and weakens the cylinder wall, so the cylinder can rupture.✓ Answer
- C.It only scorches the 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. Recovery cylinders are filled by weight to a stated maximum and are never filled completely. What is the reason?
- A.A partly filled cylinder is easier for one person to carry.
- B.Liquid expands as its temperature rises, and a liquid-full cylinder has no vapor space to absorb that expansion, so hydrostatic pressure can rupture it.✓ Answer
- C.The empty space is needed so air can be added to push the refrigerant back out.
- D.The vapor space keeps a refrigerant blend from separating.
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. What is the purpose of a pressure relief device on a refrigerant vessel?
- A.To keep the system charge accurate as ambient temperature changes.
- B.To open and relieve pressure before it exceeds what the vessel can withstand, preventing a rupture.✓ Answer
- C.To protect the compressor motor windings from overheating.
- D.To vent refrigerant during normal operation so that head pressure stays 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. A large refrigerant leak has occurred in a basement mechanical room. What is the primary hazard to a technician entering the room?
- A.Contact with the vapor causes chemical burns on exposed skin.
- B.The vapor is corrosive to the lungs at any concentration.
- C.The vapor rises and collects at the ceiling, out of the breathing zone.
- D.The vapor is heavier than air, settles in the low space and displaces oxygen, so a person can lose consciousness with little warning.✓ 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. 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 the occupant that these symptoms are unrelated to the heating system.
- B.Open a window and continue the scheduled maintenance.
- C.Change the filter and schedule a combustion check for the next visit.
- D.Get everyone into fresh air, shut the appliance down, and call emergency services or the gas utility; the appliance stays off until it is tested and corrected.✓ 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, 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. A technician confirms a cracked heat exchanger in an operating gas furnace. What is the correct action?
- A.Seal the crack with high-temperature sealant and return the furnace to service.
- B.Increase the blower speed so that any leakage is diluted.
- C.Leave it running and let the owner schedule replacement at her convenience.
- D.Shut the furnace down, lock it out, tag it and inform the owner in writing, because combustion products can enter the circulating air.✓ 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. 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 simply fail to light, so no hazard exists.
- B.The blockage will clear itself once draft is established.
- C.Blockage makes combustion products spill into the building instead of venting outdoors, releasing carbon monoxide into occupied space.✓ Answer
- D.A blocked vent only lowers efficiency and can wait until the next visit.
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. A technician must work from a ladder near overhead energized conductors. Which ladder is appropriate?
- A.Any ladder, as long as the work is finished quickly.
- B.An aluminum ladder with rubber feet, since the feet insulate it from ground.
- C.An aluminum ladder, provided the technician wears leather gloves.
- D.A fiberglass or wood ladder, because aluminum conducts electricity.✓ 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. What is the correct way to lift a heavy compressor crate from the floor?
- A.Bend at the waist with the legs straight and lift with the back.
- B.Squat with the back straight, keep the load close to the body, lift with the legs, and get help or a mechanical aid when the load is heavy or awkward.✓ Answer
- C.Lift and twist at the same time to save a step.
- D.Hold the load away from the body so the path ahead stays visible.
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. 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 the circuit is dead, because the fan can restart automatically on a pressure or defrost control.✓ Answer
- B.Switch the thermostat off, which is sufficient to prevent a restart.
- C.Hold the fan blade with a gloved hand while inspecting it.
- D.Proceed, because a fan that is not turning cannot start.
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. Before brazing a line set inside a finished building, what does safe hot-work practice require?
- A.Moving or shielding combustibles, keeping a charged fire extinguisher within reach, and maintaining a fire watch during the work and for a period afterward.✓ Answer
- B.Switching off the building's smoke detectors for the duration of the work.
- C.Wetting the surrounding drywall and leaving the area as soon as the joint is made.
- D.Nothing special, because a brazing flame is 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. 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 and consult the sheet only if someone is injured.
- B.Rely on the sheet for a similar product used last year, since cleaners are much alike.
- C.Read the current safety data sheet for that product before use, to learn its hazards, the protection required and the first-aid steps.✓ Answer
- D.Ask a supervisor for permission to see it, since the sheets are filed in the office for management use.
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. A technician must service an air handler in an unfinished attic. Which practice is correct?
- A.Walk only on the joists or truss chords, or on planking laid across them, and carry adequate lighting.✓ Answer
- B.Skip hydration and rest breaks so the job is finished before the attic gets hotter.
- C.Work by the light coming through the access hatch, to avoid carrying extra equipment.
- D.Step between the joists on the ceiling drywall, which spreads the load.
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 →

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?

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

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?

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

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

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

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

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

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

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

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

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?

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

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?

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

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

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?

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

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

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