Detectives investigating the Novichok poisonings of Charlie Rowley and Dawn Sturgess are to undertake precautionary testing of the ambulances used to treat the pair.
The Wiltshire Air Ambulance, the ambulance station, emergency vehicles and the kit worn by the first medical staff to respond to the 999 alert will be examined by experts.
Mr Rowley, 45, and Ms Sturgess, 44, fell ill in Amesbury, near Salisbury, on June 30 after being contaminated by the nerve agent.
Ms Sturgess, a mother-of-three, died eight days later having never gained consciousness. Her funeral was held on Monday.
Mr Rowley has said the nerve agent took just 15 minutes to poison Ms Sturgess after she sprayed the “oily” substance on to her wrists believing it was perfume he had given her as a gift.
It was the second nerve agent incident in four months following the case of Sergei Skripal, 67, and his daughter Yulia, 33, who were found unconscious on a park bench in Salisbury in March.
Wiltshire Police said the “highly precautionary process” was designed to ensure that no onward contamination has taken place.
The force said that to allow specialists to carry out their work the ambulance station at Semington will be closed temporarily and the air ambulance will also be tested and be unable to fly.
While the helicopter is out of action, the charity’s paramedics and doctors will instead respond to emergencies in rapid response cars.
Wiltshire Police deputy chief constable Paul Mills, who is leading the multi-agency response to the incident, said: “We are very aware that this news might cause some concern to our communities.
“The work we are undertaking forms part of the wider ongoing response to the incident and is the next logical precautionary step in the process.
“This highly precautionary activity is focused on ensuring that we take all steps necessary to consider any remediation activity which may be necessary in the longer term to further reduce any residual risk.”
David Philpott, chief executive of Wiltshire Air Ambulance, said: “As is normal procedure when our helicopter is unable to fly, our paramedics and doctors will respond to emergencies in rapid response cars, providing critical care to patients.
“We are incredibly proud to provide a lifesaving service in Wiltshire and surrounding counties and thank everyone, including our colleagues at neighbouring air ambulances, who will offer support in the short term.”
Police and crime commissioner Angus Macpherson added: “All agencies are working closely together and are working incredibly hard to ensure the safety of staff and of course of the public.
“It’s right that action is taken to rigorously and thoroughly test where the scientific advice dictates it’s appropriate to do so.
“Public safety must remain the number one priority and I am confident this is at the absolute forefront of any action taken.”