Environment, Ventilation & Hazards

Rescue Apparatus, Safety & Occupational Health

Breathing-apparatus endurance from oxygen capacity and consumption, and the accident frequency rate per million man-hours.

PART 1

Topic Breakdown & Traps

The Engineering Principle

Mine rescue relies on self-contained breathing apparatus; its endurance is the usable oxygen volume divided by the wearer's consumption rate, with a reserve held back. Safety performance is tracked statistically: the accident frequency rate normalises the number of reportable accidents to a fixed exposure (commonly per million man-hours), allowing fair comparison across operations.

The Core Formula Matrix

Apparatus duration:

t = \frac{V _{u s ab l e}}{consumption rate}

(subtract any reserve first).

Accident frequency rate:

F R = \frac{number of accidents \times 1 0 ^{6}}{man-hours worked}

The ‘IIT Traps’

⚠
Subtract the reserve before dividing by consumption — usable volume, not total.
⚠
**FR is per $1 0^{6}$ man-hours** (a common convention); keep the multiplier consistent.
⚠
Consumption is per minute — duration comes out in minutes.

PART 2

Progressive 3-Tier Question Suite

Q1BASIC1 Mark · MCQ

A breathing set has

300 L

of usable oxygen; the wearer uses

1.5 L/min

. Its duration is:

Q2MEDIUM2 Marks · NAT

A cylinder holds

360 L

but

60 L

is kept as reserve; consumption is

2 L/min

. The usable working duration is ______ min. (Round off to the nearest whole number.)

min

Q3HARD2 Marks · NAT

A mine records

6

reportable accidents over

1, 200, 000

man-hours. The accident frequency rate (per million man-hours) is ______. (Round off to two decimal places.)