As per reports, totally, nine persons died and another is injured in a work involving cleaning of sludge from an oil tank. Initially, four persons who entered for the work did not respond for few hours and three more entered to know about them.
Due to inhalation of toxic gases, persons died, as per reports.
Normally, when such works are to be carried out in confined spaces like oil tankers, closed vessels, equipment, etc, oxygen levels are to be measured and action to be taken to exhaust poisonous gases and admit air to keep oxygen levels as in the open atmosphere. Continuous exhaust is to be maintained. Where, it is not possible, they have to enter with compressed air cylinders on their back, connected to the face piece respirator. Further, there should be buddy system, i.e. for every one worker inside, there should be an equally capable person outside with safety belt extended rope in the hands of person outside; and to engage in constant communication, so that in case of any emergency, immediate rescue operations can be made.
http://indianexpress.com/article/india/maharashtra-seven-workers-die-inhaling-poisonous-gas-in-latur-district-4499670/
http://timesofindia.indiatimes.com/city/aurangabad/7-workers-die-of-suffocation-in-latur-oil-mills-chemical-tank/articleshow/56881624.cms