Safety & Service Practice — EPA 608 Practice Questions

19 questions · 17% of the Type III — Low Pressure exam

Worked questions

1. What happens if the internal pressure of a low-pressure chiller is driven past the rating of its rupture disc?

AThe purge unit automatically routes the excess non-condensables outdoors
The purge unit only handles the small quantity of non-condensable gas that collects in the condenser. It has no capacity to relieve an overpressure condition and no connection to the relief path.
BA relief valve lifts and then reseats once the pressure drops back down
Reseating is what a spring-loaded relief valve does. A rupture disc has no spring and no seat, so once the diaphragm tears it cannot close again and the machine keeps venting.
CThe compressor unloads and the machine coasts safely to a stop
Compressor controls protect the motor and the bearings, not the shell. On a machine that is shut down for service the compressor is not running at all, yet the disc can still be blown by careless heating or pressurizing.
The disc bursts and the refrigerant charge escapes to the atmosphere

Why D is correct

Unlike a spring-loaded relief valve, a rupture disc does not reseat. It is designed to burst open and stay open, protecting the shell by dumping everything inside it. Because a low-pressure machine holds a large charge, blowing the disc during careless heating or pressurizing releases that whole charge at once.

What this question is testing

This item checks whether the candidate knows the difference between a rupture disc and a reseating spring-loaded relief valve, and understands what overpressuring a low-pressure machine during service actually costs. It also tests awareness that the hazard exists on a shut-down machine, since careless heating or pressurizing during a leak test is the usual cause.

On the job

This is why crews never put an open flame or uncontrolled heat on a low-pressure chiller, and why any warming done to raise pressure is gentle and closely watched with a gauge on the machine. A blown disc means the plant loses its cooling, the owner loses a charge that is expensive and hard to source, and the crew has to write up a release. Replacing the disc and recharging the machine turns a half-day leak hunt into a multi-day job.

Memory technique

A popped balloon does not un-pop: a rupture disc bursts once and stays open until it is replaced.

Exam tip

Rupture disc equals one shot. Any answer that has it closing again, resetting, or self-limiting is describing a relief valve instead.

Where to look it up

Low-pressure appliances are protected by a rupture disc, a non-reseating device; overpressure during service causes a full-charge release.

2. How should the emergency exhaust for a chiller machine room be arranged?

ADrawing air from the ceiling and returning it to the building air handler
Ceiling level suction misses the dense vapor layer near the floor, and returning the air to the building spreads the hazard into occupied spaces.
BRecirculating room air through a carbon filter and back into the space
Carbon filters are not a control for refrigerant vapor, and recirculating the air keeps the refrigerant inside the building. The vapor would keep circulating through the space that the workers are trying to clear.
Taking suction near the floor and discharging outside the building
DBlowing outside air across the chiller with a portable fan on the floor
A portable fan stirs the room without removing anything and can push vapor toward doorways and workers instead of exhausting it.

Why C is correct

Taking suction low captures the heaviest concentration of vapor, and discharging outdoors removes it from the building rather than relocating the hazard. This arrangement is what actually clears a machine room after a release and makes it safe to re-enter after monitoring confirms the space is clean.

What this question is testing

This tests the ventilation half of machine room safety and connects it to the vapor behavior the candidate is expected to already understand. It measures whether you can connect vapor density to system design, and whether you recognize that recirculating air relocates a hazard instead of removing it.

On the job

Before you begin work that could release refrigerant, find the emergency exhaust switch and confirm the fan actually runs. Plenty of machine rooms have an exhaust system that was disconnected during a remodel or whose damper is painted shut. Also look at where the discharge lands outside, because a discharge next to a fresh air intake or a loading dock moves the problem instead of solving it, and that is worth reporting to the building owner.

Memory technique

Low in, outside out. Never send it back into the building.

Exam tip

Ventilation answers should always pull from low and discharge outside. Recirculation is never correct for refrigerant.

Where to look it up

Emergency machine room ventilation takes suction near the floor, where heavy refrigerant vapor collects, and discharges outdoors.

3. Why is a cartridge style air purifying respirator the wrong protection for entering a machine room after a chiller has released its charge?

AIt cannot be sealed to the face while safety glasses and a hard hat are being worn
Respirators are routinely worn with glasses and a hard hat, and fit problems are solved with different equipment. The failure here is in what the respirator can supply, not in how it sits with other gear.
BIts cartridges are rated only for high-pressure refrigerants and not for the low-pressure type in this machine
Cartridge ratings are not divided by refrigerant pressure class, and no cartridge of any rating puts oxygen back into the air. Matching a cartridge to the refrigerant misses the actual hazard.
CIt is too heavy to be worn safely while climbing around the machine on a ladder
Weight and ladder work are ordinary ergonomic concerns that apply to any respirator. They have nothing to do with why this one fails in an atmosphere that may be short of oxygen.
It filters contaminants from the air but supplies no oxygen, and the room may be oxygen deficient

Why D is correct

The failure is fundamental to how the respirator works: it cleans air but cannot create oxygen. In an oxygen deficient atmosphere the wearer suffocates while wearing what looks like protection, which is more dangerous than having no respirator at all because it invites entry into a space that should not be entered.

What this question is testing

This tests the reasoning behind respiratory protection selection rather than the equipment name, checking that you understand oxygen deficiency as a distinct hazard from contamination. It measures whether you distinguish contamination from oxygen deficiency, which is the distinction that determines whether a respirator protects a worker or merely encourages entry.

On the job

This mistake has killed people who thought they were protected. A worker straps on a cartridge mask, walks into a room that alarmed, feels fine for a few breaths and then goes down. Anyone entering a space after a significant release needs supplied air, an attendant outside, and a monitor reading before and during entry. If the only respirator on the truck is a cartridge unit, the correct action is to stay out and call for proper equipment.

Memory technique

Filters clean air, they do not make it. No oxygen in means no oxygen out.

Exam tip

Ask whether the hazard is contamination or oxygen deficiency. Filters handle the first and are useless against the second.

Where to look it up

Air purifying respirators cannot be used in oxygen deficient atmospheres; a large refrigerant release requires self contained breathing apparatus.

4. What personal protective equipment does a technician put on before draining liquid low-pressure refrigerant into a recovery cylinder?

AA dust mask and ordinary safety glasses
A dust mask does nothing for vapor or liquid refrigerant, and open sided safety glasses do not stop a splash from reaching the eyes.
BCotton work gloves alone, since the liquid is near room temperature
Cotton absorbs liquid refrigerant and holds it against the skin, which makes a splash worse rather than better, regardless of the liquid's temperature.
Chemical resistant gloves and splash goggles
DHearing protection and steel toed boots as the primary protection
Boots and hearing protection are ordinary jobsite equipment but they protect against hazards that have nothing to do with a refrigerant splash.

Why C is correct

Liquid refrigerant contacting skin or eyes is the hazard at this step, and the protection has to match it. Gloves of a material the refrigerant does not soak through, plus goggles that seal around the eyes, are the correct combination for a task where a fitting can spray under pressure.

What this question is testing

This tests protective equipment selection matched to the specific hazard of the task, rather than a general habit of wearing whatever is in the truck. It measures whether protective equipment is selected for the specific hazard of the task rather than worn out of general habit or convenience.

On the job

The moment of risk is when a hose is broken loose or a valve is opened faster than expected and liquid sprays sideways. Goggles that seal make the difference between a startling moment and an eye injury. Many technicians add a face shield over the goggles when breaking connections that may still hold liquid. Keep the sheet for the refrigerant handy, know where the eyewash is, and never break a connection with your face over it.

Memory technique

Liquid means splash, splash means seal. Goggles that seal and gloves that do not soak.

Exam tip

Match the equipment to the hazard described. Liquid splash means sealed goggles and chemical resistant gloves.

Where to look it up

Handling liquid refrigerant requires chemical resistant gloves and splash goggles to protect skin and eyes.

5. An oxygen monitor is used to decide whether a chiller machine room is safe to enter after a refrigerant release. Below what oxygen reading is the atmosphere treated as oxygen deficient?

ABelow twenty-one percent oxygen by volume
Twenty-one percent is normal air. Treating any reading below normal as deficient would put a room out of service for a trivial fluctuation.
Below nineteen and a half percent oxygen by volume
CBelow sixteen percent oxygen by volume
Sixteen percent is well into the range where judgment and coordination are already impaired. Waiting for that reading means people are affected before the alarm means anything.
DBelow twelve percent oxygen by volume
Twelve percent is close to the level at which a person collapses. No usable warning threshold sits that low.

Why B is correct

Nineteen and a half percent is the line at which an atmosphere is considered deficient and unsafe to enter without supplied air. It sits only a percentage point and a half below normal because the effects of low oxygen come on gradually and are not obvious to the person experiencing them. Anything below it means ventilate and re-test, or enter with supplied air.

What this question is testing

This tests recall of the exposure threshold that governs entry decisions. The exam pairs oxygen deficiency with refrigerant releases because displacement, rather than toxicity, is what usually harms people in a machine room.

On the job

Chiller machine rooms are frequently below grade with poor natural ventilation, and the vapor from these refrigerants is heavy and settles. A monitor at the door is what tells a crew whether the exhaust has done its job. The number matters because operators will ask whether twenty percent is good enough, and the answer is that twenty is acceptable while nineteen is not, and that the difference is deliberately set with a margin.

Memory technique

Twenty-one normal, nineteen and a half is the line. Barely a point and a half of margin, which is why it is taken seriously.

Exam tip

Air is twenty-one percent oxygen. Deficient starts at nineteen and a half, not at some dramatic lower figure.

Where to look it up

An atmosphere below nineteen and a half percent oxygen by volume is oxygen deficient and unsafe to enter without supplied air.

6. A chiller has been standing under a dry nitrogen holding charge and a technician now has to climb inside the shell. What has to be done to the space first?

It has to be ventilated with fresh air and the oxygen content verified before entry
BIt has to be brought to atmospheric pressure and left open for the shift before entry
Opening a vessel does not ventilate it. Heavy gas layers sit undisturbed inside a shell for a long time with no air movement to displace them.
CIt has to be warmed with the water pumps so that the nitrogen rises out of the shell
Warm water in the tubes does nothing to exchange the atmosphere inside the shell, and nitrogen does not conveniently rise out of an opening.
DIt has to be swept with dry refrigerant vapor so that the nitrogen is displaced downward
Sweeping with refrigerant vapor replaces one asphyxiant with another and wastes refrigerant doing it.

Why A is correct

The hazard is displacement rather than toxicity, and nitrogen gives no warning at all because it does not smell, irritate or trigger the body's response to suffocation. Only forced ventilation puts air back into the shell, and only a meter proves it worked. Testing before entry and continuing to monitor during it is the practice that makes the entry survivable.

What this question is testing

This tests confined space judgment applied to a situation created by good refrigerant practice. The exam includes it because the same nitrogen holding charge that protects a machine creates a lethal atmosphere inside it.

On the job

Nitrogen asphyxiation kills people in industrial plants every year, and it does it fast, quietly and often to the person who goes in to help. Chiller work invites it because a nitrogen holding charge is standard practice on a machine waiting for parts. The routine is fixed: purge with air using a blower, meter the space, keep the blower running, post an attendant with the means to get help, and never reach into a vessel that has not been tested.

Memory technique

Nitrogen is not poison, it is absence. You do not smell it because there is nothing there to smell.

Exam tip

Nitrogen leaves no smell and no warning. Ventilate, test for oxygen, then enter with an attendant.

Where to look it up

A vessel that has held nitrogen contains no oxygen; it must be ventilated and its atmosphere tested before entry.

7. After a release in a chiller machine room the exhaust has been running for an hour and nobody at the door can smell anything unusual. What does that tell the crew about re-entering?

AThat the room is clear, because these refrigerants have a sharp odor at hazardous levels
The odor of these refrigerants is faint and easy to miss, and people stop noticing it quickly. It gives no useful warning of a hazardous concentration.
BThat the room is clear, because an hour of exhaust exceeds the required ventilation period
No fixed ventilation period clears a room, because neither the size of the release nor the room's actual air change rate is known.
CThat the room is probably clear, so entry with a cartridge respirator is now reasonable
A cartridge respirator filters contaminants but supplies no oxygen, so it is the wrong protection for a room that may still be oxygen short.
That nothing has been established, because the decision has to rest on meter readings

Why D is correct

Warning properties describe whether a substance announces itself before it becomes dangerous, and these refrigerants have almost none. That is precisely why a machine room holding them carries fixed monitors. Re-entry after a release is a measurement decision: oxygen at or above the safe level, and refrigerant vapor below the exposure limit, both read on an instrument.

What this question is testing

This tests resistance to a plausible but unsupported conclusion. The exam raises warning properties because candidates who think of refrigerant hazards in terms of smell will make exactly this call in the field.

On the job

This is the argument that happens at the machine room door after every significant release, usually with somebody impatient to get the machine back on. The answer that ends it is the meter. Crews that do this work carry a portable monitor rather than relying on the fixed one, because the fixed sensor is in one place and the vapor is heavy and pools. Readings get written down with the time, which also settles the question later.

Memory technique

Your nose is not a monitor. It has no alarm and no calibration date.

Exam tip

No smell proves nothing with these refrigerants. Only an instrument reading makes a room safe to enter.

Where to look it up

Low-pressure refrigerants have poor warning properties; re-entry after a release is decided by oxygen and vapor monitor readings.

8. A technician wants to open a fitting on a chiller's purge unit while the machine is running, on the assumption that the whole machine is under a vacuum. What is wrong with that assumption?

AThe purge unit holds its own separate charge that is always above atmospheric pressure
The purge does not hold a separate refrigerant charge of its own; what is inside it came from the chiller.
BThe purge unit's suction line is the one part of the machine that runs at chilled water pressure
The purge is connected to the refrigerant side of the machine and never sees chilled water pressure.
The purge takes suction from the condenser, which is above atmospheric while the machine runs
DThe purge unit stores refrigerant under pressure only during the few seconds of each cycle
Whatever is in the purge drum stays there between cycles, and it is at condenser pressure rather than briefly pressurized.

Why C is correct

The pressure profile across a running machine is what decides this. The condenser sits above atmospheric at load, and the purge is connected to it, so purge piping is under positive pressure whenever the machine is running. Assuming the whole machine is under a vacuum is the mistake, and it produces a release directly into an occupied machine room.

What this question is testing

This tests the pressure profile applied to personal safety rather than to leak direction. The exam reuses the same fact in both settings because candidates tend to learn the vacuum story as a blanket statement about the whole machine.

On the job

Technicians who have absorbed the idea that chillers run in a vacuum sometimes treat any fitting on the machine as safe to crack, and the condenser end of a loaded machine will prove them wrong immediately. The habit that avoids it is simple: gauge the section before opening it, whatever you believe about the machine. Purge work is scheduled with the machine down, the purge isolated and its contents recovered.

Memory technique

The purge lives on the warm end of the machine, where the pressure pushes out rather than pulling in.

Exam tip

Vacuum on the cold end, positive pressure on the hot end. Gauge the section before you open it.

Where to look it up

The condenser of a running low-pressure chiller is slightly above atmospheric, and the purge unit is connected to it.

11 more in the bank

Answers and explanations for these are in the app.

What respiratory equipment must a technician wear to enter a machine room after a large refrigerant release?
What monitoring equipment belongs in a machine room that houses a large low-pressure chiller?
Where does refrigerant vapor collect if a chiller releases a large part of its charge inside a machine room?
Why must the relief piping downstream of a chiller's rupture disc never be plugged, valved shut or blocked?
What has to be done before a technician climbs inside a chiller water box to plug a leaking tube?
Where does a technician look up the exposure limit and first aid information for the refrigerant in a particular machine?
A machine room holds chillers charged with R-123, and the vapor monitor has to be set with the refrigerant's exposure limit in mind. What is the manufacturer's allowable exposure limit for R-123 as an eight hour average?
Liquid low-pressure refrigerant has spilled onto a machine room floor and is standing in a pool. What is the correct handling of that liquid?
A low-pressure chiller's rupture disc has a discharge line running from it. Where does that line have to terminate?
A refrigerant vapor detector in a chiller machine room reaches its alarm level. Besides sounding, what is that alarm expected to do?
A chiller machine room's refrigerant and oxygen sensors have been in place for several years with no service recorded. What does that mean for the protection they provide?

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Safety & Service Practice — EPA 608 Practice Questions

Worked questions

1. What happens if the internal pressure of a low-pressure chiller is driven past the rating of its rupture disc?

2. How should the emergency exhaust for a chiller machine room be arranged?

3. Why is a cartridge style air purifying respirator the wrong protection for entering a machine room after a chiller has released its charge?

4. What personal protective equipment does a technician put on before draining liquid low-pressure refrigerant into a recovery cylinder?

5. An oxygen monitor is used to decide whether a chiller machine room is safe to enter after a refrigerant release. Below what oxygen reading is the atmosphere treated as oxygen deficient?

6. A chiller has been standing under a dry nitrogen holding charge and a technician now has to climb inside the shell. What has to be done to the space first?

7. After a release in a chiller machine room the exhaust has been running for an hour and nobody at the door can smell anything unusual. What does that tell the crew about re-entering?

8. A technician wants to open a fitting on a chiller's purge unit while the machine is running, on the assumption that the whole machine is under a vacuum. What is wrong with that assumption?

11 more in the bank

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