Underground, every ordinary hazard changes category
That is the thing to understand before sitting this chapter. A small fire on the surface is escaped by walking away in any direction. The same fire underground fills the only route the crew can use, so a bin fire between the workface and the portal is immediately life threatening regardless of how little there is to burn.
A leaking pipe becomes an atmosphere. A person who is unwell is a long way from help through a single route. Water arriving unexpectedly can rise faster than people can walk out. None of these are exotic hazards; they are ordinary ones with the escape removed.
Atmosphere is the subject that runs through everything
Methane comes out of the ground itself in many formations and collects in the crown, which is not where anybody checks by instinct. Diesel plant consumes oxygen and produces carbon monoxide in a space with limited dilution. Argon and carbon dioxide from welding sink and fill the bottom of a chamber with no smell and no warning at all.
That is why ventilation underground is a life safety system rather than a comfort one, and why its failure is a reason to withdraw rather than a reason to work faster. A gas detector confirms the atmosphere has already gone bad; the ventilation is what stops it.
Half of confined space deaths are rescuers
That single statistic explains why the chapter puts so much weight on rehearsed rescue arrangements rather than on detection. Somebody who goes in after a colleague without equipment is responding to exactly the atmosphere that dropped the first person, and the outcome is two casualties instead of one.
It is also why tally systems matter. In an emergency the first question is how many people are still inside and where, and there is no time to reconstruct that from memory.
Ground support is the structure
Above ground a failed prop usually gives warning and affects one element. Underground the support is the structure, there is no redundancy, and everybody in the drive is downstream of it. Freshly exposed ground stands unsupported for a stand up time that depends entirely on the formation, and in poor ground that is measured in minutes.
Falling behind the excavation and support cycle is therefore a stop rather than a delay, which is a distinction the chapter tests directly.
The thin pool is the one worth revising
Two papers of K questions from a bank of N share about K squared over N. Because a specialist paper draws from a large core pool and a smaller subject pool, the combined figure looks better than the tunnelling slice does. Both are reported above the test, and the revision mode targets what you keep getting wrong.
Common questions
Why is a large tunnel still a confined space?
Because the definition is about restricted egress plus a foreseeable specified risk, not about size. A tunnel can be tall enough to drive a lorry through and still trap everybody inside it behind a single smoke logged route. Size changes how long the air lasts, not whether the space is confined.
What does an oxygen reading of 19% mean?
That something has displaced or consumed the oxygen, because normal air is 20.9%. It is not within tolerance, it is evidence. Whatever displaced the oxygen may itself be the hazard, and a small depletion can become a large one quickly.
Why does hydrogen sulphide get people who can smell it?
Because at dangerous concentrations it paralyses the sense of smell. Low levels smell strongly of rotten eggs; high levels smell of nothing. Somebody relying on their nose concludes the problem has cleared at the exact moment it has become lethal.
What is a self rescuer for?
To get you out, and nothing else. It provides breathable air or filters carbon monoxide for long enough to walk the escape route at a steady pace. It is not working breathing apparatus and treating it as such ends when the set does.
How many marks do I need to pass?
Forty five out of fifty in forty five minutes, the same as every operatives and specialist test. Five wrong is the whole allowance. Thirty five questions come from the core chapters and fifteen from tunnelling, and the tunnelling fifteen are unusually unforgiving to revise for, because underground almost every ordinary hazard changes category rather than changing degree.
Are these the real tunnelling questions?
No. CITB sells its live bank, and reproducing it would be somebody else’s copyright. The tunnelling questions here are written from free HSE guidance, principally the confined spaces material along with the fire safety and temporary works pages, and every answer links to the source. That is worth more than a real question would be: a wrong answer here sends you to the paragraph that explains it.
Is my progress separate from the other tests?
Yes, in your browser and nowhere else. Each paper has its own key, so the tunnelling record is not disturbed by sitting the operatives test. The specialist pool is twenty eight questions and fifteen appear per paper, so about eight repeat on a second attempt. The page reports that on its own instead of folding it into a total for all fifty, which would read more comfortably than it deserves.