Reply To: Reporting clearance air test results – your views sought

Home Forums Members Only Forums Technical Discussion Reporting clearance air test results – your views sought Reply To: Reporting clearance air test results – your views sought

#4399

Rereading HSG 248 (Ed 2, July 2021),  several times the LOQ for clearance testing is expressed as <0.010 f/ml (A1.7, A1.41, Table 5.2 etc…)

The footnote to table A1.1 states ‘ The reported concentration should not imply greater accuracy than can be justified by the LOQ eg a 480-litre volume sample with 200 fields counted will be reported as <0.01 f/ml or rounded to two decimal places if _> 0.01 f/ml. ‘

The calculated concentration should be reported to 3 decimal places,  but the reported result should always be reported as <0.01 f/ml or if greater then reported as described above.  After all our customers, the Duty Holder, are familiar with <0.01 f/ml and implied safety aspect of reoccupying an area after works.  If we start implying  a greater precision, then we are going to confuse our  customers.

One last comment the LOQ is based on 20 fibres counted in 200 fields.  In recent experience we rarely count 20 fibres at stage 3.  Are asbestos removal control measures getting better?

Do we need a research to establish what is the fibre concentration post asbestos removal?  Just maybe we are already witnessing the reduction of the clearance indicator, but we just can’t demonstrate it.  Just a thought.