At around 6.30 p.m., a fire broke out in an empty 1,200m² poultry-farming building used to fatten up broiler chickens on a farm. The frontages of the building, which was built 28 years ago, were made from asbestos-cement sandwich panels. The roof was also made from asbestos-cement (sheeting) and featured photovoltaic panels on one side. The day before, the farmer had prepared the hen house for the scheduled arrival of chicks the next day. The ground was covered with 6t of chopped straw. Before the Covid-19 pandemic lockdown periods, the farmer used to hire a fogging company to disinfect the hen house. Faced with the partial shutdown of the company used previously, the farmer did the job on their own and lit 3 disinfectant smoke bombs (bactericidal, fungicidal, yeasticidal) set up on the ground on a slate. They removed straw from a diameter of about 1m around each smoke bomb. They left the hen house. 15 min later, the fire broke out.

The firefighters encountered response issues due to the presence of a power line over the building. The electricity company was contacted to shut off the power supply. The farm did not have a firefighting water tank. Firefighters put out the fire. A specialist company demolished and removed asbestos from the building.

There was an expert investigation of the area affected by the incident. The following hypotheses were ruled out:

• arson by a third party;
• fire of external origin, from the technical room, the rooftop photovoltaic system, or due to running of different motors in the building;

The farmer stated that they had not complied with the recommended distances for the removal of combustibles (in this case straw) specified in the smoke bombs’ safety data sheet (SDS). The removal diameter specified in the SDS was 3m, but the farmer only removed straw from an area with a 1m diameter. However, it appears unlikely that the radiation from the smoke bomb could have set fire to the chopped straw. The following hypotheses concerning the straw coming into contact with the smoke bombs set up on the ground are:

• incomplete removal of straw due to the quality of the ground (compacted earth) and tools used (broom);
• The farmer may have displaced straw when they moved between the smoke bombs to light them;
• air intake by one of the fans may have increased the change of straw being blown onto the smoke bombs.

It is recommended to set up smoke bombs on a non-combustible stand, raised off the ground and with a separating edge. The farmer has also set up a 120m³ flexible firefighting water storage tank near the building.