A tracer trial to study the movement of airborne material in the urban environment will be taking place in the London Borough of Westminster shortly.
The trial will consist of small releases of a harmless, odourless gas at various locations within Marylebone and the monitoring of how it disperses within the local area.
It is expected to be carried out over a 48 hour period. The exact timing and precise location will be dependent on suitable meteorological conditions. The trials aim to improve contingency planning in the unlikely event of a chemical, biological, radiological or nuclear release. It follows similar trials that were carried out in May and June of 2007 and is not a response to any specific threat.