Two hazards belong to this trade and to nothing else on site
The first is refrigerant. Most of it is heavier than air, so a leak fills a plant room from the floor up while the air at head height is still fine. There is no smell and no sensation, so the first sign is somebody losing consciousness, and the person most at risk is the one kneeling to find the leak.
The second is cooling water. Cooling towers and evaporative condensers generate aerosol from warm water, and they are the classic source of legionella outbreaks that kill members of the public rather than workers. That is why they are notifiable and why the water treatment regime is continuous rather than annual.
Life above the ceiling
A ceiling grid carries tiles, not people, and the fall through is onto whatever is below. The void is also where old insulation, live cables and fire stopping live, so the hazards stack up in a space nobody can see into until they are in it.
A refurbished ceiling below tells you nothing about what is above it. Sprayed coatings and board around structural steel are exactly what an HVAC route runs past, which is why checking the asbestos information comes before the ladder rather than after the first surprise.
Fans keep turning after the power goes off
A large impeller runs down slowly and will still take a hand, and access doors get opened by somebody who has switched the unit off at the local switch. Local switches get restored by facilities staff who want the air on, which is why lock off is the control and switching off is not.
Commissioning is the same problem in a different form: it is the point where equipment moves for the first time, and the people at risk are the ones who were inside it a moment ago.
Fire stopping is part of the install, not somebody else’s job
A duct through a compartment wall is a hole in the fire strategy of the building. An unsealed penetration lets smoke into the escape route, and it becomes invisible the moment the ceiling goes back. That is why it is checked before closing up rather than at handover.
It is the operatives test plus a chapter
Roughly seven questions in ten are core material from the operatives test, so the core areas are what will fail you if they are shaky. The score separates HVAC and ductwork out as its own line so you can tell which problem you have.
Sitting it twice, and what the second paper shows you
Two papers of K questions from a bank of N share about K squared over N. The subject pool is smaller than the core, so it repeats sooner than the combined figure suggests. Both numbers are reported above the test, and the revision mode targets what you keep getting wrong.
Common questions
Why is a refrigerant leak dangerous if the gas is not toxic?
Because most refrigerants are heavier than air and displace oxygen at low level. Asphyxiation gives no warning at all: nothing to smell, nothing to feel, until somebody loses consciousness. A plant room can be perfectly breathable at head height and lethal at floor level where an engineer is kneeling.
Why are cooling towers notifiable?
Because they have caused legionella outbreaks that killed people who never entered the building. The aerosol travels on the wind. Notification to the local authority exists so that when an outbreak happens the authorities know where every tower in the area is, which is how sources get traced.
Is a large plenum still a confined space?
Yes, if the egress is restricted and there is a specified risk. Size does not remove either. The specific risks in a plenum are the fan starting and the atmosphere in a space that has been sealed, and the part to plan is the rescue, because getting an unconscious person out of a duct is not something two colleagues improvise.
Does brazing indoors need extraction?
Yes. Welding and brazing fume is now treated as a health risk requiring control indoors regardless of duration, and brazing fluxes can contain fluorides while filler metals may contain cadmium or silver. Nitrogen purging inside the pipe is a separate requirement, and it is a quality one as much as a safety one.
What score do I need to pass?
Forty five of fifty in forty five minutes, so five wrong answers is the lot. Fifteen of them come from HVAC and ductwork and thirty five from the core operatives chapters. The trade fifteen carry two hazards that belong to nothing else on site, refrigerant pooling at floor level and cooling water growing legionella, and neither behaves the way general site experience suggests.
Are these the actual questions from the HVAC paper?
No. CITB sells the live bank in GT100 and publishes none of it. These questions are written from free HSE guidance, mostly the confined spaces, pressure systems and legionella material with work at height behind it, and each answer links to its source. On refrigerant and cooling towers that matters, because the correct answer is counterintuitive often enough to want checking.
Does this share progress with the other mocks?
Yes, under its own key in your browser, separately from every other test on the site and with no account anywhere. On the specialist side the pool is twenty eight and each paper draws fifteen, so roughly eight repeat on a second attempt. The result reports that figure on its own rather than inside a total for all fifty, which would make a second run look more like practice than it is.