Thieves stole a £6,000 decontamination shower unit, used by workmen in Peterborough Road, Carshalton.
The white unit, which has an OCS logo on the side, went missing on Wednesday, October 15.
Someone living in the area told police they saw two men removing it between 8pm and 9pm.
One of them is described as white with shaved mousey brown hair, and aged between 35 and 45.
He is also said to be about 5ft 8ins, and wearing a high visibility jacket.
The witness was unable to describe the second man.
The decontamination unit is said to resemble a burger van, and was first based in Peterborough Road on October 13.
If you have any information call Sutton police on 101, quoting crime reference number no: 4010885/14.
You can also call Crimestoppers anonymously on 0800 555 111.
Have you ever witnessed a theft or burglary? Call the news desk on 020 8722 6358, or email tom.gillespie@london.newsquest.co.uk
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here