CSCS Excavations & Confined Spaces Questions
Trench support, inspections and confined-space entry.
These questions cover excavations & confined spaces for the CITB Health, Safety and Environment (HS&E) test, the exam UK construction workers pass to get a CSCS card.
Excavations & Confined Spaces: practice quiz
- 20 questions · 30 minutes · pass mark 90%
- Answers and explanations are shown at the end, with every question to review.
- A fresh 20 questions every time, drawn from all 114 in this topic's bank. Includes 2 select-two questions and 1 picture question, as in the real test.
- About 90 seconds a question, against about 54 in the real test, so there is time to think.
10 sample Excavations & Confined Spaces questions and answers
These 10 come from the 114 questions the practice quiz above draws from, written out with the correct answer and the reasoning behind it. Read them through when you want to revise rather than test yourself.
1. Supports have been provided in an excavation. Under CDM 2015, what has to happen before construction work is carried out in it?
Answer: A competent person must inspect it at the start of the shift in which the work is done
- A) A competent person must inspect it at the start of the shift in which the work is done (correct answer)
- B) The excavation must be re-measured and its depth written into the site diary by the engineer
- C) A permit to dig must be signed off by the client before anyone enters the excavation
- D) The excavator operator must confirm the ground has not moved since it was first dug
Why: Regulation 22(4)(a) of CDM 2015 says construction work must not be carried out in such an excavation unless a competent person has inspected it at the start of the shift in which the work is to be carried out, after any event likely to have affected its strength or stability, and after any material unintentionally falls or is dislodged. Note the wording of regulation 22: the duties are written in the passive, so they do not attach to one job title such as the site manager.
2. Loss of consciousness from a rise in body temperature is what, under the Regulations?
Answer: A specified risk, which can make an enclosed space a confined space
- A) A specified risk, which can make an enclosed space a confined space (correct answer)
- B) A matter dealt with only by the welfare requirements of CDM 2015
- C) Outside the scope of the Confined Spaces Regulations 1997 altogether
- D) A risk only where the work lasts longer than two hours at a time
Why: The specified risk definition expressly includes the loss of consciousness of any person at work arising from an increase in body temperature.
3. Why does Schedule 3 of CDM 2015 matter?
Answer: It flags work involving particular risks for the construction phase plan
- A) It sets out all the fees payable for a notifiable construction project
- B) It lists the substances that may not be used on a construction site
- C) It lists the qualifications that a competent person is required to hold
- D) It flags work involving particular risks for the construction phase plan (correct answer)
Why: Schedule 3 is referenced by regulation 12(2), which concerns the construction phase plan. Work with particular risks needs specific planning attention.
4. Testing the atmosphere shows the oxygen level is low. What does that indicate?
Answer: That a specified risk is present and entry controls are needed
- A) That the space is safe provided the work is completed quickly
- B) That a specified risk is present and entry controls are needed (correct answer)
- C) That the space is not a confined space under the Regulations
- D) That a dust mask is enough protection before entering the space
Why: Lack of oxygen causing loss of consciousness or asphyxiation is a specified risk, which brings the entry prohibition in regulation 4 and the rescue duty in regulation 5 into play.
5. Trench support is being put in as a trench is dug. What does HSE construction guidance say about working in relation to that support?
Answer: Never work ahead of the support or remove it prematurely
- A) Never work ahead of the support or remove it prematurely (correct answer)
- B) Work ahead of it if the ground looks firm and dry on the day
- C) Take it out early once the trench reaches its final depth
- D) Leave it until the end of the shift, then fit it all in one go
Why: HSG150 paragraph 344 says support should be installed without delay as the excavation progresses, and that you should never work ahead of the support or remove it prematurely.
6. An excavation has no support fitted. In which situations does HSE construction guidance say it will be safe without support?
Answer: Only if its sides are battered back enough, or it is in sound rock
- A) Only if it is less than a metre deep, or the weather stays dry
- B) Only if it is fenced off, or it will be open for under a day
- C) Only if a banksman watches it, or the plant is kept 2 m away
- D) Only if its sides are battered back enough, or it is in sound rock (correct answer)
Why: HSG150 paragraph 345 says an unsupported excavation will be safe without support only if its sides are battered back sufficiently or it is in sound rock.
7. Before excavation work begins, what does HSE say commercial clients must give contractors information about?
Answer: Ground conditions, underground structures or water courses, and existing services
- A) The working hours, the site parking plan and the canteen opening times
- B) The total cost of the work, the payment terms and the agreed completion date
- C) Ground conditions, underground structures or water courses, and existing services (correct answer)
- D) The excavator make and model, the operator's licence and the hire firm's insurance
Why: HSE's excavations guidance says commercial clients must provide relevant information on ground conditions, underground structures or water courses, and the location of existing services, for use in planning the dig.
8. An HSE inspector asks to see extracts from an excavation inspection report. What does CDM 2015 require?
Answer: The extracts or copies the inspector asks for must be sent to the inspector
- A) The report must be destroyed once the excavation has been backfilled
- B) The extracts or copies the inspector asks for must be sent to the inspector (correct answer)
- C) The request can be refused, as reports are private to the contractor and client
- D) Copies are sent if the work was found safe, and held back if not
Why: Regulation 24(3)(b) of CDM 2015 requires the person on whose behalf the inspection was carried out to send the inspector such extracts from or copies of the report as the inspector requires.
9. A chamber below ground is close to a landfill site. What does L101 say about contamination of below-ground spaces?
Answer: They can be contaminated by installations many metres away
- A) They can be contaminated by installations many metres away (correct answer)
- B) Sources must be directly next to the chamber to affect it
- C) Landfill gas cannot pass through the ground into a chamber
- D) Below-ground spaces are protected by the soil around them
Why: L101 paragraph 57 says below-ground confined spaces are at particular risk because they can be contaminated by substances from installations many metres away.
10. A large confined space has several entry points and is about to be boxed up after work. What must the safe system of work make sure of?
Answer: That everyone has left the space before it is closed up
- A) That the covers are refitted in their numbered order
- B) That the last person out signs the site diary
- C) That the space is pressure washed one last time before closing
- D) That everyone has left the space before it is closed up (correct answer)
Why: L101 paragraph 124 says the safe system of work should ensure that everyone has left the confined space during boxing-up, particularly where the space is complicated with many entry and exit points.
What this topic covers in the CSCS test
These two subjects sit together because they fail the same way, fast and with almost no warning. An unsupported trench side can bury you in seconds, and the air in a confined space can be lethal before you notice anything is wrong. Two HSE points are worth carrying into the exam: no ground can be relied upon to stand unsupported, and the people killed in confined spaces include those who went in to rescue someone else.
- Why excavations collapse, and how shoring, trench boxes and battering prevent it
- Who inspects an excavation, when, and what must be recorded
- Edge protection, spoil heaps, and keeping plant back from the edge
- Safe access and egress, and why petrol and diesel engines are kept out
- Buried services: plans, cable locating devices and safe digging practice
- What makes a space a confined space, and the risks that define one
- The Confined Spaces Regulations 1997: atmosphere testing, ventilation, permits and rescue
Key facts worth memorising
- A cubic metre of soil can weigh over 1.5 tonnes
- That is why a collapse is so often fatal even in a shallow trench, and why HSE says no ground can be relied upon to stand unsupported in all circumstances.
- Inspection at the start of every shift
- Regulation 22 of CDM 2015 requires a competent person to inspect a supported or battered excavation at the start of the shift, after any event likely to affect its stability, and after any fall of material.
- A written report within 24 hours
- Under regulation 24 of CDM 2015, an inspector who is not satisfied must say so before the end of the shift and provide a written report within 24 hours.
- Ladders reach 1 metre above the landing
- A ladder used for access must stand on a firm level base, be secured against slipping and extend at least 1 metre above the landing place unless there is a suitable alternative handhold.
- Locate, mark, then dig carefully
- HSE's sequence is plans first, then a locating device used frequently and repeatedly, then trial holes by hand, digging alongside the service rather than above it and using insulated tools near cables.
- A confined space is defined by risk, not size
- It is a space that is enclosed or largely enclosed with a foreseeable risk of fire, explosion, loss of consciousness, asphyxiation or drowning, so a large silo counts and so does an unventilated pit.
What people get wrong
A shallow trench does not need support.
Depth is not the test. With a cubic metre of soil weighing over 1.5 tonnes it takes very little material to crush someone. Decide the support before you dig and have it on site before work starts.
If a workmate goes down in a confined space, you get them out.
This is how confined spaces kill more than one person at a time. HSE says the dead include untrained rescuers, and that relying on the emergency services is not enough. Raise the alarm and use the rescue arrangements that had to exist before the work began.
The service drawings show you where the cables are.
Plans give only an indication of the location and number of buried services, and HSE says tracing with a locating device afterwards is essential. Marker tape works the same way: it tells you something is close, not exactly where.
One gas test at the start covers you for the day.
HSE warns that a confined space being safe one day does not mean it always will be. Test before entry and keep monitoring, and if the alarm sounds you leave first and work out why afterwards. Never try to sweeten the air with oxygen, which sharply raises the fire risk.
Answering these questions in the test
Almost every scenario here has one answer that means getting out or staying out, and that is the one to take. Supports moving, a gas alarm sounding, an odd smell, a colleague collapsing: none of these are assessed from the inside. Also watch the difference between a warning and a control. Marker tape, a gas alarm and a lookout all tell you something. What keeps you alive is the trench support, the tested atmosphere, the barrier at the edge and the rescue plan made before anyone went in.
Sources
Written from the following. Where a figure could not be verified against one of these, it has been left out rather than approximated. Our sources and methodology explains how we date and re-check them. Spotted something wrong? Report an error and we will fix it.
- hse.gov.uk/construction/safetytopics/excavations.htm
- hse.gov.uk/construction/safetytopics/underground.htm
- legislation.gov.uk/uksi/2015/51/regulation/22/made
- legislation.gov.uk/uksi/2015/51/regulation/24/made
- hse.gov.uk/confinedspace/introduction.htm
- hse.gov.uk/confinedspace/legislation.htm
- hse.gov.uk/pubns/indg258.pdf
- legislation.gov.uk/uksi/1997/1713/contents/made
Topics that come up alongside excavations & confined spaces
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