How to calculate the oxygen level drop in a room if any gas cylinder leaks in to the atmosphere.

The air around us is a mixture of gases, mainly nitrogen and oxygen, but containing much smaller amounts of water vapor, argon, and carbon dioxide, and very small amounts of other gases. According to the Occupational Safety and Health Administration, OSHA, determined the optimal range of oxygen in the air for humans runs between 19.5 and 23.5 percent. As we aware that lower oxygen content (depending upon %) may have various effects in our human body.

So, when gas cylinder is stored in area/gases are used in an area, it is very important to predict the concentration of gas present in that area for carrying out adequate safety precaution. The calculation are as follows

Assumption/Conditions:

1.      Volume of the room                            = 165 Cu.m

2.      Gas stored                                           :   Nitrogen in cylinder

3.      No air exchange rate in the room         :   0

4.      Weight of N2 in cylinder                                              = 16 kg

Calculation

Density of air at 30°C(our environment temp)  = 1.1644 kg/Cu.m

Mass of air in the room                                    = 165 * 1.1644             = 192.126 kg

Molecular weight of air                                               = 29

So, Number of kg-moles of air                                   = 192.126/29

= 6.625034

Since the volume ratio is the same as mole ratio for gases,

Therefore

Number of kg-moles of N2               =          6.625034*.78 (78 % of N2 in atmosphere)

=          5.167527

Number of kg-moles that would add if leaked from the cylinder is = 16(weight of N2 in cylinder)/28

= 0.57.

Total kg-moles of Nitrogen in the room = 5.16752 + 0.57 = 5.737527

If the released volume of N2 is added to denominator, then the % of N2 in air (after Nitrogen release is)

= (5.737527 / 6.625034+0.57) *100         = 79.7429 %

The oxygen % in air is reduces to = 19.287 % which below 19.5%. so we can go for any of the below said recommendation

Note : More over the above said will come if equal dispersion happens & in case of any jet leakage the oxygen level near the leakage area will be low which increases the risk.

Recommendation:

o fixed point oxygen monitoring need to be carried out & display of that alarm need to be given outside the room to indicate if oxygen level drop inside the room.

o Cylinders should be moved to well-ventilated area after its usage.

o Hose & pipeline (rigid & flexible) should be checked daily.