BS 8468-3.2:2020 pdf download.Respiratory protective devices for use against chemical, biological, radiological and nuclear (CBRN) agents Part 3.2: Air-purifying devices incorporating a hood for escape - - Specification.
Three filters shall be tested for each test representative agent TRA) and against each test condition, as given in 5.5.2.1 after the complete device has been preconditioned in accordance with BS EN 403:2004, 7.4. The gas/vapour test challenges and breakthrough concentrations shown in Table 2 shall be used to establish the filter breakthrough time and thus classification.
NOTE 2 The TRAs have been chosen to represent families of potential CBRN threat agents.
Irrespective of the device classification, the high-flow rate performance test, in accordance with 5.5.2.2. shall have a duration of not less than 5 mm, using the filter test challenge agents and breakthrough concentrations given in Table 2.
5.5.2 Test conditions
5.5.2.1 Gas capacity test
Gas capacity tests shall be performed with the test agent drawn through the hirer at a continuous flow rate of (64 ±1) 1/mm, both at a temperature of (25 ±2.5) °C and a relatively humidity (RH) of (25 i5)%, and at a temperature of (25 ±2.5) °C and (80 i5)% relative humidity.
The breakthrough time achieved shall determine the filter classification.
Specimen orientation shall be such that the gas flows horizontally and in line with the direction of minimum bed depth of the filter. A gas stream shall not directly impact on to the filter face.
NOTE Filters can be tested separatefr or as part of the complete device. When tested as part of the complete device, it might be necessaiy to use special techniques to ensure correct sealing and correct filter orientation in the test apparatus.
If it is possible that a single filter of a multiple filter device can be used alone, the requirements of the full flow rate for the tests, as stated in this British Standard, shall be met.
NOTE 2 The TRAs have been chosen to represent families of potential CBRN threat agents.
Irrespective of the device classification, the high-flow rate performance test, in accordance with 5.5.2.2. shall have a duration of not less than 5 mm, using the filter test challenge agents and breakthrough concentrations given in Table 2.
5.5.2 Test conditions
5.5.2.1 Gas capacity test
Gas capacity tests shall be performed with the test agent drawn through the hirer at a continuous flow rate of (64 ±1) 1/mm, both at a temperature of (25 ±2.5) °C and a relatively humidity (RH) of (25 i5)%, and at a temperature of (25 ±2.5) °C and (80 i5)% relative humidity.
The breakthrough time achieved shall determine the filter classification.
Specimen orientation shall be such that the gas flows horizontally and in line with the direction of minimum bed depth of the filter. A gas stream shall not directly impact on to the filter face.
NOTE Filters can be tested separatefr or as part of the complete device. When tested as part of the complete device, it might be necessaiy to use special techniques to ensure correct sealing and correct filter orientation in the test apparatus.
If it is possible that a single filter of a multiple filter device can be used alone, the requirements of the full flow rate for the tests, as stated in this British Standard, shall be met.
