The normal air requirement for an average person is 10 cubic feet per minute.
If workers must work in the confined space, the space must be flushed with compressed air for at least 4 hours continuously and be certified safe by a qualified gas tester. For example, if a fractional column has a base of 10 meters in dia and a height of 90 meters. We shall need a compressor that can produce one cubic meter of air per second at 150 psi to flush the column continuously for 4 hours. This inlet air supply must be plugged at the lowest point at the base of the column with a one-inch connection to the compressor outlet. The outlet for the air to escape must be at the highest point of the column.
Do not enter without breathing apparatus if the oxygen level is 19.5% or less by volume. However, if the level is 23.5% or more by volume, it is also not safe to enter because at this level, it is explosive.
Combustible organic compounds inside a tank can be as high as 30%. A combustible gas meter analyzer must be used to confirm the volume of the combustible gas.
Many years ago, a technician was inspecting a vessel for petrol storage. He was carrying a lighted electric bulb. When the lighted bulb was accidentally broken in that vessel, he died on the spot because of the violent explosion.
The most recent work-related death because of negligence was documented in 2005 when an engineer went inside a compartment on board a ship for inspection. He died in that compartment. The hatches for ventilation were all closed. The next time you are asked to enter a confined space, ask yourself the following questions:
Who are the people qualified to approve permit for vessels and confined space entry?
Are the gas testers qualified?
Are the instruments used for the testing in good condition?