Part III - Historical Survey of the Porton Down Service Volunteer ...

staff member and moved to sampling positions. Volunteers stood in a line, 5 yards apart, and
remained there until the cloud generated by the shell had passed over them. The distance
from the sampling positions to the point at which the shell was burst was chosen, based on
measurements of temperature and wind speed, so that the maximum accumulated exposure
experienced by volunteers would not exceed 12 mg.min/m 3 .
Trial 1. Ten volunteers took part. Three shells were exploded one at a time: one
shell with GB stabilised with triethylamine, one with GB alone, and one with water.
GB (from the first two shells) at the sampling points varied from 0.35 - 1.6 mg.min/m 3 .
Trial 2. Eight volunteers took part. Four shells were exploded one at a time: three
had the same fillings as Trial 1, the fourth contained GB stabilised with ammonia. GB
at seven of the sampling points varied from less than 0.35 mg.min/m 3 to
1.4 mg.min/m 3 . The volunteer at the remaining sampling position was exposed to
10.5 mg.min/m 3 .
The volunteers who participated in the trials were able to distinguish by smell the shells
containing GB from those containing water. The stabilisers seemed to make the smell
appreciably stronger. Another set of field trials was conducted in February 1952 [38] and the
procedure adopted in the December 1951 field trials was used again. Four trials were carried
out, with a wider variety of stabilisers.
Trial 1. Twelve volunteers took part. Four shells were used: one with water, one
with GB alone, one with GB stabilised by triethylamine and one with GB stabilised by
diethylamine. The exposure levels in this trial were 0.4 - 1 mg.min/m 3 .
Trial 2. Ten volunteers participated. Four shells with the same fillings as Trial 1
were used. Exposure levels were 0.4 - 1.7 mg.min/m 3 .
Trial 3. Fifteen volunteers participated. Three shells were used, one with water, one
with GB alone and one with GB stabilised by methyl-N-morpholine. Exposures were
0.4 - 1.1 mg.min/m 3 .
Trial 4. Fifteen volunteers took part. Three shells with the same filling as Trial 3
were used. Exposure levels were 0.5 - 3.2 mg.min/m 3 .
As in the December trials, volunteers were able to detect GB by smell. The volunteers found
little difference between the smell of GB alone and of stabilised GB. This was thought by
Porton to be somewhat suspicious as it "suggested the possibility of collusion having
occurred between observers" [39]. Therefore a further set of trials was carried out March
1952 but in this trial each volunteer was accompanied at his sampling point by a "responsible
scientist", thus eliminating the possibility of collusion. Apart from this pairing arrangement,
the procedure adopted for the trials was the same as before.
• Two shells were used: one with GB alone and one with GB stabilised by
triethylamine.
• Nineteen sampling positions were used. At 18 of them a volunteer was
accompanied by a member of Porton staff. At the nineteenth, two volunteers and
one member of staff were used. Exposures experienced were 0.4 - 1.7
mg.min/m 3 .
No significant difference was found between the smell of GB alone and stabilised GB. The
trial confirmed that GB dispersed explosively by a shell could be detected by smell at
concentrations of 0.5 - 0.8 mg/m 3 [39]. Trials were held later in March to find out if GB
dispersed as a spray, rather than in an explosion, could be smelled [40]. Ten volunteers
participated. GB alone and stabilised GB were released as spray individually. The duration
of each exposure was about 50 seconds and the levels varied from 0.4 to 3.1 mg.min/m 3 .
Volunteers were unable to detect any difference in smell between the two sprays. However,
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