An explosion occurred at 3 pm on the roof-terrace of an apartment hotel in Paris’ 12th arrondissement, comprising: a basement level, a ground floor, 8 floors, and a roof-terrace containing the building’s operating equipment: mechanical ventilation, 2 smoke extraction fans, 1 waste bin extraction unit, air conditioning/refrigeration installations, an 800-litre buffer tank assembled with a heating resistance to prevent the hydraulic network from freezing during winter, and a power and remote control cabinet dedicated to the refrigeration equipment. The blast could be heard throughout the district. The 800-litre tank at the origin of the accident, wound up destroying in its wake part of the facilities (ventilation casing, hydraulic networks), before smashing into and ripping the metal siding panels on a nearby building housing a telecommunications company and then falling onto the delivery zone of an adjacent hotel, 150 m from its initial location. Sheet metal fragments and miscellaneous debris were projected over an extensive perimeter, causing broken windows on the hotel facade.

The blast of this explosion also moved the 2 cooling units, one of which was left upright 1 m off its support, as its movement was stopped by the outer terrace guardrail and the hydraulic pipes.

Fire-fighters and police were notified, and the police architect visited the site. Gas and electricity utility services verified that the installations would not jeopardise the intervention team; the general circuit-breaker was cut. The apartment hotel was evacuated and hoots rehoused in other residences owned by this Paris Region group.

The next day, the police department’s central laboratory took samples and scrapings on components of both the refrigeration unit and buffer tank.

On Monday 10th March, several specialised contractors restored the installations, including: reparation of damaged and/or severed cables on the smoke extraction equipment, reinstallation of the cooling unit that had shifted off its concrete base, placement of protective netting over all machinery so as to prevent debris from being ejected and injuring passers-by, re-flocking of the fresh air duct on the forced air system in order to respect the fire resistance threshold, restart of the “alarm/alert” system, resetting of the fire protection flaps and smoke removal hatches.

An inspection office along with the fire-fighters tested the smoke extraction alarms and alerts as of 3 pm the same day, thereby noting that the fresh air duct was once again flocked. With these trials deemed satisfactory, the residence was re-opened for business. The laboratory conducted an investigation to determine the causes and circumstances surrounding this accident.