Fire in a fertilisers plant

A gas leakage (approximately 70% hydrogen, 21% nitrogen and the rest carbon monoxide and other impurities) occurred at the connection between a temperature measurement casing and a flange in the carbonization workshop cleaning tower. The leakage was reported to the plant leader, who issued the request to the workers to use iron cards and rubber plates to plug the leak. The operation failed and the leakage continued.
At 17:00, at the request of the plant leader, the workers used a tire inner tube to wrap the leak. However, due to the high pressures in the tower the high-speed by which the gas was released, and the fact that that the rubber is an electrical isolator, electrostatic sparks were produced, which ignited the gas and started a fire.

The direct cause of this accident was the production of sparks when attempting to stop the leak. The cause of the leak is unknown.
The indirect causes of the accident were, (i) the plant operator violated rules and regulations, issuing requests disregarding health and safety; (ii) the worker also did not take effective safety measures; (iii) a lack of emergency procedures, and probably a lack of risk assessment.

temperature probe casing, flange, carbonisation unit

two fatalities and an economic loss of more than 43k Euro

According to the source (see References), the following safety actions and measures should be in place and followed when trying to stop a leakage:
[HIAD operator Note: the following list of measures does not explicitly state the most obvious and most effective measure is the depressurisation of the leaking system/facility before starting any type of repair work. Measure (1) implies it, very generically].
(1) Safety technical measures and safety technical specifications such as fire prevention, explosion prevention, corrosion prevention, and heat radiation prevention shall be designed, implemented and enforced.
(2) The intervention team shall consist of a small number of very competent workers, with a strong sense of responsibility, familiar with the working conditions of the equipment and be equipped with one or two supervisors.
(3) These workers shall wear protection equipment appropriated for the working conditions of the facility, as prescribed by the regulations and have prepared the required supplies of repairing/replacing tools and equipment.
(4) Clean up the leakage plugging site, and take protective measures such as evacuation, drainage, ventilation and cover up if necessary for dangerous media according to their conditions and the nature of their media.
(5) To plug releases of flammable and/or explosive media, the welding plugging method shall be avoided as far as possible. The use of tools and operation methods that may cause sparks is prohibited. Copper tools, air guns, drills should be used, electrical equipment and electrical tools shall be avoided.
(6) Loose and tight bolts, union joints and other parts, after cleaning with kerosene, rust remover, etc., apply graphite and molybdenum disulphide to lubricate the thread, so that it can be operated gently and slowly to avoid bolts and wire buckles breaking.
(7) A platform should be set up for high-altitude work, and a lift, / machine, and crane should be used as a platform if the platform cannot be set up. Warning boards shall be used.
(8) Underwater plugging should comply with underwater operation regulations. The team shall wear impervious diving suits and ensure that the snorkel is intact and that safety measures are reliable.
(9) When operating indoors, in trenches, in underground and/or containers, preventive and rescue measures shall be in place to avoid intoxication and suffocation. The measures shall be in place and tested before accessing pits, wells, cellars or containers.
(10) The worker or the team of workers shall carry out the work according to the plan decided in advance and adopt a cautious approach. In case of abnormal phenomena during execution of the plan, they should not improvise or act upon subjective, individual opinion: they shall take time to reflect jointly, discuss and identify the best way forward.