http://www.ehstoday.com/construction/worker-severely-burned-when-trapped-fiery-underground-duct?NL=OH-05&Issue=OH-05_20171116_OH-05_712&sfvc4enews=42&cl=article_4&utm_rid=CPG03000007741031&utm_campaign=23112&utm_medium=email&elq2=4c69ad8c5a1d4c0f9872eb2a45dd0031
A worker suffered third degree burns due to a fire while working inside a duct that had rich oxygen.
The contractor was charged for safety lapses in confined space work, i.e. failure to ensure work area air monitoring, mechanical ventilation.
Many do not know the hazards of oxygen above atmospheric levels of 21% v/v. One should not think that compressed air and compressed oxygen are same.
Dress soaked in oxygen can catch fire easily. Materials burn easily in high oxygen conditions.
Higher oxygen levels can cause damage to lungs and eyes.
That's the reason why safety professionals ask for measuring and finding reasons for oxygen levels in work area which are not at 21% v/v.
Even if it is low, even slightly below 21% also, one should not think it is okay, because the difference can be some toxic/poisonous and pose health hazard. Similarly, for higher levels.
Then, we should ensure supply of fresh air (not oxygen) in the confined space work area. Generally, we supply air into the work area for 24 hours before work. Again, the work atmosphere will be measured for safe condition before permitting the persons inside.
Then buddy system also is to be ensured.