Confined Space Operations Flashcards

Under the Confined Spaces Regulations 1997, what is the first principle a specialist supervisor must apply before allowing entry into a confined space?

Answer: Avoid entry to the confined space wherever reasonably practicable

Regulation 4(1) of the Confined Spaces Regulations 1997 states that no person at work shall enter a confined space to carry out work unless it is not reasonably practicable to achieve the objective without entry. Avoidance is always the first principle.

What minimum oxygen level in a confined space would require the use of breathing apparatus before a specialist operative can enter?

Answer: Below 19.5%

Normal atmospheric oxygen is 20.9%. An oxygen level below 19.5% is considered oxygen-deficient and requires the use of self-contained breathing apparatus (SCBA) or supplied air respirators. Levels below 16% can cause impaired judgement, and below 6% can be immediately fatal.

A specialist team is about to enter a sewer for maintenance work. Which of the following gases poses the greatest immediate risk of explosion?

Answer: Methane

Methane (CH4) is highly flammable and forms explosive mixtures with air at concentrations between 5% and 15% (its lower and upper explosive limits). While hydrogen sulphide is extremely toxic, methane presents the greatest explosion risk in sewer environments. Carbon dioxide and nitrogen are asphyxiants, not explosive.

How often must continuous atmospheric monitoring be maintained during specialist work inside a confined space?

Answer: Continuously throughout the entire period of occupation

Atmospheric conditions in confined spaces can change rapidly due to work activities (welding, painting, cutting), disturbance of materials, or ingress of gases. Continuous monitoring throughout occupation is essential to detect any deterioration and trigger evacuation before workers are endangered.

What is the primary role of the 'top man' (attendant) stationed outside a confined space during specialist operations?

Answer: To maintain communication with entrants and initiate emergency rescue procedures if needed

The attendant (top man) maintains continuous communication with those inside the confined space, monitors their condition, controls entry and exit, and is responsible for raising the alarm and initiating the emergency rescue plan if a problem occurs. They must never enter the space themselves to attempt rescue.

A specialist supervisor discovers that the confined space entry permit has expired but workers are still inside completing their task. What is the correct action?

Answer: Withdraw all personnel immediately and re-assess before issuing a new permit

An expired permit means the documented risk assessment and control measures are no longer valid. All workers must be withdrawn immediately. A new assessment of conditions must be carried out and a fresh permit issued before re-entry. Verbal extensions are not acceptable as they bypass the formal safety checks.