1. Gas freeing is essential before entering empty tank.
2. Manhole doors to be opened for at least 24 hours before entry.
3. Forced ventilation with air duct, to be done with electric blower, for at least 24 hours.
4. With forced exhausting system, minimum of 2 air changes should be completed during
that time. [For every dangerous space, 10 to 20 air changes are necessary.]
5. After thorough ventilation, tank atmosphere tested for any toxic or explosive gases, by
invited Chemist or with Safety Lamp before entering. [Flame will burn clearly, if free
from foul gases. Faint blue cap will show presence of explosive gases. If burning black
or flame goes out, it shows presence of CO₂ gas, which is fatal to life].
When tested by Chemist, TLV must be taken as a standard.
6. When the tank is gas free, following LSA to be carried or kept ready, when entering.
a) Lifeline or harness to be put on.
b) Spark proof hand torch to be brought in.
c) BA set to be kept ready.
d) Resuscitation equipment to be kept ready.
e) Have rescue team, readily available and properly led.
f) Competent person, stand-by at entrance.
g) Agree a communication system, before entry.
h) Have adequate illumination.