Evacuation around ETH Zurich: Hundreds of residents must make way for chlorine trifluoride disposal

Evacuation procedure and affected area

Residents are to be informed and asked to leave their apartments via megaphone on the street, as well as by police officers in the stairwells going from door to door. In addition, an information notice has been attached to all properties, a cantonal police media spokesman told Keystone-SDA. The affected residents had also been informed directly by personal letter at the end of May about the operation on Sunday.

Specialists from Schutz und Rettung of the City of Zurich are also deployed. The surrounding streets will be closed to car and tram traffic. During the operation, there will be temporary road closures, restrictions on public transport and diversions for private traffic.

Origin and properties of chlorine trifluoride

The cantonal police have declared the area around the main building of ETH Zurich a restricted zone for the following hours. Several ETH buildings are also affected by the evacuation – laboratories and halls may not be used. Those affected would be informed by SMS, the cantonal police spokesman added.

The trigger for the measures is a gas cylinder containing chlorine trifluoride. In one of the university's buildings, ETH had stored a gas cylinder with «a potentially dangerous chemical substance», as the cantonal police announced in a communiqué: chlorine trifluoride. This had previously been stored in a access-restricted laboratory of ETH Zurich and is now to be disposed of.

Transport and disposal by specialist company

The laboratory that handled it no longer exists. The substance now has to be disposed of. The chlorine trifluoride was used in the past for the analysis of rock samples, as ETH explained. The chemical was used in geological research.

Chlorine trifluoride is quite something. The chemical is so aggressive that it can eat away silicates and break stable quartz bonds. It sets things on fire that are actually considered non-flammable. It is explosive. And it is extremely toxic. The gas is considered one of the most dangerous chemicals of all, is toxic and can ignite on contact.

For the transport of this single cylinder by a German specialist company, additional safety measures had become necessary. The gas cylinder will leave its previous location around 12 noon and be stored airtight in a special container. The cargo will then be ready for transport to Germany. The chemical will be disposed of by a German specialist company.

Reactions and apology from ETH

The evacuation is a precautionary measure, ETH and the cantonal police emphasized. They expect this delicate phase to be over in about an hour, a spokesman said on Friday. The deployment of the security forces is scheduled to last until 4:30 p.m. at the latest. However, it is to be expected that the evacuated residents will be allowed to return to their homes earlier.

The safety of the residents is the top priority, the press spokesman said. But no one will be forced to leave their own home. To his knowledge, there has never been a comparable operation in the City of Zurich. Around 100 responses had been received, with only one critical inquiry.

ETH Zurich apologizes to the neighborhood for the circumstances. The university has offered those affected a voucher: for an admission to the zoo including food and drink.