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Safety & Service Practice — EPA 608 Practice Questions

18 questions · 17% of the Type II — High Pressure exam

Worked questions

1. A full nitrogen cylinder can sit at well over two thousand pounds per square inch, while the components in a comfort cooling system are rated for a small fraction of that. What does that difference require of the technician?

  • The cylinder must be fed through a pressure regulator so only a controlled test pressure ever reaches the system
  • BThe cylinder valve should be cracked open slowly instead, since opening it gradually limits the pressure delivered

    A valve controls flow, not pressure. Opening it slowly changes how fast the system fills, not the pressure it eventually reaches, which is full cylinder pressure.

  • CThe nitrogen should be discharged into a length of hose first so it loses pressure before entering the system

    Gas does not lose pressure by traveling through a hose. A hose full of high-pressure nitrogen simply delivers high-pressure nitrogen at the other end, and the hose itself may not be rated for it.

  • DThe system should be left connected to the recovery machine so the machine can absorb any excess pressure

    A recovery machine is not a relief device and is not rated to absorb cylinder pressure. Connecting it in that situation puts the machine at risk too.

Why A is correct

A regulator is a pressure-reducing device with a set outlet. It maintains the pressure the technician dialed in even as cylinder pressure falls, which is the only reliable way to keep a huge supply pressure from reaching equipment rated for far less.

What this question is testing

This item tests whether the candidate understands the difference between controlling flow and controlling pressure, and why the regulator rather than technique is the safeguard.

On the job

Regulators for nitrogen come with a high-pressure gauge reading cylinder contents and a low-pressure gauge reading the delivered pressure, and many field regulators include a relief on the low side for exactly this reason. Techs check that the adjusting knob is backed all the way out before opening the cylinder valve, then bring the outlet pressure up slowly. Cracking a cylinder valve straight into a system is how accumulators split and relief devices lift.

Memory technique

A valve controls how fast, a regulator controls how hard. You need the regulator.

Exam tip

Slow valve opening never substitutes for a regulator. Any answer implying a technician can control pressure by hand is wrong.

Where to look it up

Dry nitrogen must be delivered through a pressure regulator; cylinder pressure vastly exceeds system component ratings.

2. A technician runs a small flow of dry nitrogen through the tubing while brazing new line set into a refrigeration system. What does that flow accomplish?

  • AIt cools the joint so the filler metal sets up faster after the torch is pulled away from the copper

    The flow is far too small to cool anything, and quick cooling of a brazed joint is undesirable in any case. The nitrogen is there to keep air off the inside of the copper.

  • It keeps oxygen away from the hot copper so black oxide scale does not form inside the tubing
  • CIt raises pressure inside the tubing so the filler metal is pushed into the joint gap

    Filler metal is drawn into a properly heated, properly fitted gap by capillary action. Pressure behind the joint would blow molten filler back out of it rather than pushing it in.

  • DIt tests the joint for leaks at the same moment the joint is being made and heated

    Leak testing is a separate step, done after the joint is complete and cool, with the system brought to a controlled test pressure. A purge flow tells the technician nothing about tightness.

Why B is correct

Oxide scale requires oxygen and heat. Removing the oxygen from inside the tube by displacing it with an inert gas prevents the reaction entirely, which keeps the inside of the new tubing clean and keeps loose scale out of the system's metering devices and screens.

What this question is testing

The candidate must state the purpose of a brazing purge and distinguish it from cooling, from pressurizing, and from leak testing, all of which sound plausible to someone who has only seen the nitrogen bottle at the job.

On the job

The setup is a regulator turned down very low, a hose into one end of the tubing, and an open end somewhere downstream so the nitrogen has a path out. Techs who cap both ends end up with pressure that blows molten filler out of the joint, which is dangerous and ruins the work. It is one of the clearest quality markers on an installation: cut open a drier on a no-purge job and the black flakes tell the story.

Memory technique

Flow it, do not blow it. The nitrogen is there to chase out the oxygen, not to push on anything.

Exam tip

Purge nitrogen flows, it does not push. Small flow, open path out, no pressure behind the joint.

Where to look it up

Flowing dry nitrogen through tubing during brazing prevents internal cupric oxide scale formation. An open vent path is required.

3. A technician is disconnecting service hoses that may still hold liquid refrigerant under pressure. What personal protection belongs on that task?

  • Safety glasses and gloves, because liquid refrigerant striking skin or eyes causes freeze burns
  • BA respirator, because refrigerant vapor is absorbed through the lungs as a systemic poison in seconds

    Common refrigerants are not systemic poisons taken up through the lungs in this way. The inhalation hazard is oxygen displacement in a confined space, which ventilation and monitoring address.

  • CRubber-soled boots, because escaping refrigerant carries an electrical charge to ground

    Refrigerant carries no electrical charge. Electrical protection is a real and separate concern on a service call, but it has nothing to do with breaking a pressurized hose connection loose.

  • DA face shield alone, since gloves reduce the feel needed to break a fitting loose cleanly

    Gloves are exactly what protects the hands doing the work, and a liquid jet reaches them first. Trading them for a face shield leaves the most exposed part of the body uncovered.

Why A is correct

The hazard from escaping liquid refrigerant is thermal. Rapid boiling pulls heat out of skin and eye tissue fast enough to cause a freeze injury on contact, so eye protection and gloves are the protection that matches the actual risk.

What this question is testing

The candidate must identify the correct protective equipment and, more importantly, the actual mechanism of injury, distinguishing a thermal hazard from inhalation and electrical hazards that belong to other tasks.

On the job

The classic injury happens with a manifold set that still holds liquid in the hoses after charging. The technician cracks a fitting expecting a puff of vapor and gets a jet of liquid across a bare hand or into an unprotected eye. Good practice is to recover the hose contents rather than purging them, keep glasses on for the whole job, and treat any hose that has seen liquid as still charged until proven otherwise.

Memory technique

Liquid out of a hose is instant winter. Glasses on the eyes, gloves on the hands, every time.

Exam tip

Liquid refrigerant means freeze burns, which means glasses and gloves. Respirators belong to the confined space question, not this one.

Where to look it up

Liquid refrigerant causes frostbite on contact; eye and hand protection are required when handling refrigerant under pressure.

4. A large quantity of refrigerant has leaked into a basement equipment room where no ventilation has been running. What is the hazard facing the first person who opens that door?

  • AThe refrigerant will have turned to an acid mist while it pooled, and that mist burns exposed skin on contact

    Acid forms when refrigerant decomposes at high temperature, over a torch flame or a hot surface. Refrigerant pooling in a cool basement has nothing to break it down, so no acid mist is waiting at the door.

  • The vapor is heavier than air and settles low in the room, displacing the oxygen a person needs to breathe
  • CThe vapor will ignite from any spark thrown by the electrical equipment running in the room

    The common refrigerants in this equipment are not readily ignited under these conditions, and framing the hazard as fire sends the responder looking for ignition sources while the danger is the air itself.

  • DThe vapor raises the pressure inside the closed room enough to cause ear injury on the way in

    A leak does not pressurize a room in any measurable way. The room stays at atmospheric pressure with the wrong gas filling the lower part of it, so nothing about entering threatens the ears.

Why B is correct

These vapors are denser than air and accumulate at the lowest point in a space. Because they simply take the place of air, the danger is a lack of oxygen rather than any toxic effect, and it develops without a strong odor or any other warning to the person entering.

What this question is testing

This item checks understanding of vapor density and the asphyxiation mechanism, and whether the candidate can pick the real hazard out of a list of plausible-sounding alternatives.

On the job

Machinery rooms and basements are built with vapor sensors and exhaust fans for exactly this reason, and those systems are worth checking before entering rather than after. The same hazard shows up in walk-in freezers with a leaking evaporator and in elevator pits under a leaking line. The habit is to open the space up, run ventilation, and wait, and to have a second person outside the room who knows you went in.

Memory technique

Refrigerant sinks. It fills the basement from the floor up and takes the air with it.

Exam tip

The refrigerant inhalation hazard on this exam is oxygen displacement in a low or enclosed space. Ventilate first, enter second.

Where to look it up

Refrigerant vapors are heavier than air and accumulate in low areas, displacing oxygen. Ventilation is required before entry.

5. A technician has to leave refrigerant and nitrogen cylinders on a roof for several hours during a long change-out. How should those cylinders be handled while they sit there?

  • ALaid down flat on the roof deck so that wind and foot traffic cannot tip them over

    On its side a cylinder's relief device may sit in liquid instead of vapor, which changes how it behaves in an overpressure event. Cylinders are stored and used standing upright and secured.

  • BSet close against the unit's hot condenser coil so they stay warm and hold enough pressure to charge with

    Deliberately warming a cylinder raises the pressure inside it, which is the hazard being guarded against. Heat is what overfilled cylinders fail from, and a running condenser is a heat source.

  • CLeft with the valve cracked slightly open so internal pressure cannot build while they sit

    An open valve is a deliberate release, which is prohibited, and it empties the cylinder besides. Pressure is managed by keeping the cylinder cool and correctly filled, not by venting it.

  • Stood upright and secured against tipping, out of direct sun so heat does not drive the pressure up

Why D is correct

Upright placement keeps the pressure relief device in contact with vapor rather than liquid, securing prevents a fall that can break off a valve, and keeping cylinders out of the sun holds the liquid temperature down so the internal pressure stays within the range the cylinder and its relief device were designed around.

What this question is testing

This item checks knowledge of correct cylinder handling and the reasoning behind it, including the relationship between temperature and cylinder pressure and the function of the relief device.

On the job

Roof work adds hazards that ground-level work does not have: no shade, hot membrane surfaces that can exceed air temperature by a wide margin, wind, and a long carry back to the truck. Crews stage cylinders against a curb or a rail with a strap, throw a light cover over them, and keep the number of cylinders on the roof to what the job actually needs. Fall protection near the edge and a secured ladder belong on the same checklist.

Memory technique

Stand them up, strap them down, keep them cool, keep them shut.

Exam tip

Upright, secured, shaded, valve closed. Any option that heats a cylinder or opens its valve is wrong on both safety and regulatory grounds.

Where to look it up

Cylinders are stored and used upright and secured; heat raises internal pressure. Venting refrigerant to atmosphere is prohibited.

6. A technician is removing a compressor that suffered a motor burnout, and the oil coming out of it is dark and smells sour. What precautions belong on that job?

  • Gloves and eye protection together with good ventilation, because the oil and residue carry acid and irritating breakdown products
  • BA grounding strap, because a burned motor leaves a static charge in the oil that can discharge when the shell is opened

    Oil does not hold a static charge from a burned motor, and grounding addresses an electrical hazard that is gone once the unit is disconnected. It does nothing about the corrosive residue actually in the oil.

  • CNothing beyond the usual gloves and glasses, because the acid in the oil neutralizes as soon as the system is opened to the atmosphere

    Acid in burnout oil does not neutralize on contact with air. That belief is what leads technicians to handle the oil bare-handed and to skip the filter driers the cleanup procedure depends on.

  • DA respirator only, because the breakdown residue is hazardous to breathe but does no harm to the skin it touches

    The residue is corrosive to skin as well as irritating to breathe. Protecting only the lungs leaves hands and eyes exposed to the material that is easiest to get on them while pulling the compressor.

Why A is correct

Burnout residue is acidic and irritating, and it is present in the oil, on internal surfaces and in the vapor coming out of the opened system. Skin contact, eye contact and inhalation are all real routes of exposure, so hand and eye protection plus ventilation cover the actual hazards of the job.

What this question is testing

The item checks whether the candidate knows what a burnout produces chemically and can select protection matched to a corrosive contact and inhalation hazard.

On the job

Cleanup goes well beyond personal protection: the contaminated refrigerant goes to its own cylinder and then to a reclaimer, the liquid line drier gets replaced, a suction line drier with access ports goes in so the pressure drop can be checked, the system gets evacuated with nitrogen sweeps, and the oil is disposed of properly rather than poured into a shop drum. An acid test kit tells the technician what they are dealing with before the new compressor goes in.

Memory technique

Black oil, sour smell, acid. Gloves and glasses before anything else comes apart.

Exam tip

Burnout equals acid. Any answer that treats the residue as inert or self-neutralizing is wrong.

Where to look it up

Motor burnout produces acidic decomposition products in the oil and refrigerant; skin, eye and respiratory protection plus ventilation are required.

7. A refrigerant cylinder is connected to the high side of a system for liquid charging and the compressor is then started with the cylinder valve still open. What is the danger in that arrangement?

  • AThe cylinder will empty into the system faster than the metering device allows

    Charging faster than a metering device would pass is exactly why high side liquid charging is done with the compressor off. The reverse flow is the hazard once it runs.

  • BThe refrigerant will fractionate as it passes backward through the hose

    Fractionation happens when vapor is drawn off a blend. Liquid moving through a hose in either direction does not separate the components.

  • Discharge pressure can push back into the cylinder and overfill it
  • DThe liquid line will collapse under the vacuum the compressor creates

    Refrigerant tubing does not collapse under any pressure a compressor develops. The pressure difference here drives flow, it does not crush the line.

Why C is correct

With the compressor running, discharge pressure exceeds cylinder pressure, so the flow reverses and refrigerant is pushed back into the cylinder. A cylinder taking a return flow can pass its fill limit without the technician noticing, and it is being warmed at the same time. Liquid charging on the high side is therefore done with the system off, and the cylinder valve is closed before startup.

What this question is testing

This tests understanding of which way refrigerant flows when the machine starts, applied to a charging practice technicians use daily. The hazard follows directly from the pressures involved, which is the reasoning the exam is checking.

On the job

This bites on change-outs where one technician is charging and another switches the disconnect back on, and the first warning is a cylinder that has gained weight on the scale. Keeping a hand on the cylinder valve, and treating the scale reading as something to watch rather than glance at, catches it. Overfilled cylinders are dangerous well after the job ends, since they travel in a hot truck and sit in a hot shop.

Memory technique

Start the compressor and the high side becomes uphill. Your cylinder is now at the bottom of the hill.

Exam tip

Ask which side is higher once the compressor runs. Anything connected to the high side becomes a destination, not a source.

Where to look it up

Charge liquid into the high side only with the compressor off, and close the cylinder valve before startup.

11 more in the bank

Answers and explanations for these are in the app.

  • A technician needs to pressurize an R-410A system to search for a leak after a repair. Which gas source belongs on that job and why?
  • A technician is adding R-410A to a running split system that is low on charge. What is the danger of dumping liquid refrigerant straight into the suction service valve?
  • A technician is out of nitrogen and considers using the oxygen cylinder from the torch outfit to pressurize a system for a leak search. Why must that never be done?
  • Before putting a torch to a leaking line, a technician confirms the refrigerant has been recovered and that the tubing has an open path to atmosphere. Why does that open path matter so much?
  • A technician notices a sharp, acrid odor while brazing near a line that still holds a trace of refrigerant. What does that odor signal?
  • A technician opens the electrical panel of a rooftop unit after pulling and locking out the disconnect at the curb. What inside that panel still has to be treated as live?
  • Charging is going slowly because a refrigerant cylinder is cold, and a helper suggests warming the cylinder up. Which method is acceptable?
  • A technician runs out of room in the recovery cylinder partway through a job and notices an empty disposable refrigerant jug on the truck. Why can that jug not be used to hold the rest of the recovered charge?
  • A technician is sent to work in a closed machinery room fitted with a refrigerant vapor sensor tied to an exhaust fan. What is the right approach before entering and working in that space?
  • A technician has to reach past a compressor that has been running under load to get at a valve behind it. What is the hazard presented by the compressor's discharge line?
  • A technician wants to remove the Schrader cores from a rooftop unit's service ports so that evacuation will go faster. What has to be true, or what tool is needed, before a core is unscrewed?

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