The Home Office would like to inform Parliament of a series of tracer gas trials that are due to commence in the Westminster area as part of the Home Office's chemical, biological, radiological and nuclear (CBRN) Science and Technology Programme.

The trials will improve our understanding of the movement of air-borne material in the urban environment, and will enable enhancements in public protection to be developed.

The work is part of the Home Office's commitment to improve security and counter-terrorism. It will improve the UK's ability to deal with the consequences of a CBRN release through an increased knowledge of the dispersion of material in the urban environment. This knowledge will assist in planning for CBRN response and in public and emergency responder safety.

The trials will involve the release of small amounts of non-toxic, odourless gases in the Marylebone area of Westminster starting from 20 May 2007. The trials will run for a four to six-week period during which time information leaflets will be available to the public. The tracer trials will pose no adverse effect on public health or on the daily routine in the Marylebone area of Westminster.

Similar tracer trials, led by the Department for Transport, were undertaken on 25 March and 1 April 2007 as part of a study looking at air movement within the London Underground environment.