THINK DETAILS FOR EXPLOSIVITY

                         Is the concentration > 10% of LEL?

The so-called “do-nothing” action in reality means a great deal and involves monitoring the situation as it evolves during the incident.

As a rule of thumb, when the concentration of a gas or vapour in air is over 10% of the LEL (lower explosion limit) care must be taken to avoid an explosion.  One should continue on-site monitoring with extreme caution if higher levels are encountered (10%-20% of the LEL).  At levels higher than >20% of the LEL there is an explosion hazard and one should withdraw from the area immediately.