§ Mr. Livingstone
To ask the Secretary of State for Defence, pursuant to his answer of 16 March,Official Report, column 718, in which years the Chemical and Biological Defence Establishment carried out studies on the protection afforded by the S6 respirator when worn by human beings; what these studies entailed; what was the conclusion of these studies; which chemical warfare agents were used in these studies; and when the S6 respirator was issued for and withdrawn from use by the armed forces. 
§ Mr. Freeman
This is a matter for the chief executive of the Defence Evaluation and Research Agency. I have therefore asked him to reply.
Letter from J. Chisholm to Mr. Ken Livingstone, dated 5 July 1995:Your question to the Secretary of State for Defence asking, pursuant to his Answer of 16th March, about work at the Chemical and Biological Defence Establishment (CBDE) on the S6 respirator, has been passed to me to reply as the Chief Executive of the Defence Evaluation and Research Agency (DERA) which, since April, includes CBDE as one of its divisions.2. The S6 respirator development programme commenced in the early 1950's. During this time a number of user trials were conducted by Service Units. These user trials were, however, not under the control of the then Chemical Defence Establishment (CDE) although personnel from CDE provided general advice on planning the trials and, on occasion, assisted the Unit personnel in conducting the trial. During these acceptability trials the respirator fit was assessed using the Unit's exposure chamber in which chloroacetophenone, a tear gas, was routinely employed. No studies 277W involving the use of chemical or biological warfare agents were conducted to assess the protection afforded by the S6 respirator.3. In addition, to the user acceptability trials conducted by Service Units, studies were carried out between 1954 and 1964 at CDE using Service volunteers wearing the S6. These studies involved the use of simulant materials such a Bacillus globigii, a common organism found in hay and grassland throughout the UK and judged to present no hazard to health; common salt aerosols; and CS, a tear gas. Further studies measured the ingress of nitrogen into the respirator.4. The S6 respirator was first issued to the Armed Forces in 1966 and its withdrawal from service began in 1986.5. I hope this information helpful.