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

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
5.1 General
The complete device for use against CBRN agents shall be an air-purifying escape device incorporating a hood conforming to BS EN 403:2004, except for the requirements in BS EN 403:2004,6.10 and 6.11 for both types and except for the requirements in BS EN 403:2004,6.14,6.19 and6.21 for Type 1.
The complete device for use against CBRN agents shall also meet the requirements specified in 5.2 to5.6 of this British Standard.
In addition, Type 1 devices shall pass the single-burner, moving specimen test, method 3 inaccordance with BS EN 13274-4:2001.
In all tests, all test samples shall meet the requirements.5.2Preconditioning
Samples shall be preconditioned in accordance with BS EN 403:2004,7.4 prior to visual inspection,testing for inward leakage and chemical agent permeation and penetration.
5.3Visual inspection
Visual inspection shall be in accordance with BS 8468-8:2020,Clause 6. A minimum of two samplesshall be inspected.
5.4Inward leakage
The maximum inward leakage in the breathing zone shall be 0.1% when tested as a complete systemin accordance with BS EN 403:2004,7.6.1, with 10 test subjects, except that the choice of test agentshall be determined in accordance with BSEN 13274-1,8.1, according to the requirements for
combined filtering devices.
The maximum inward leakage in the ocular zone shall be 0.67% when tested as a complete systemin accordance with BS EN 403:2004,7.6.1, with 10 test subjects, except that the choice of test agentshall be determined in accordance with BS EN 13274-1,8.1, according to the requirements for combined filtering devices.
5.5 Filters – Gas/vapour element
5.5.1 Test agents – Challenge concentrations and breakthrough concentrations Filters for air-purifying devices incorporating a hood shall be classified according to the breakthroughtimes achieved in the laboratory tests as given in Table 1.
NOTE 1The device classification, once established through testing, may be termed the Designated Duration (t) ofthe device. This terminology is used in 5.7,chemical agent permeation and penetration testing.
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 withBSEN403:2004,7.4.The gas/vapour test challenges and breakthrough concentrations shown inTable 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 with5.5.2.2, shall have a duration of not less than 5 min, using the filter test challenge agents andbreakthrough 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 filter at a continuousflow rate of (64 ±1)1/min, both at a temperature of (25±2.5)°C and a relatively humidity (RH) of(25 ±5)%, and at a temperature of (25 ±2.5) °C and (80 ±5)% 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 ofminimum bed depth of the filter. A gas stream shall not directly impact on to the filter face.
NOTE Filters can be tested separately or as part of the complete device. When tested as part of the completedevice, it might be necessary to use special techniques to ensure correct sealing and correct filter orientation in thetest apparatus.
lf it is possible that a single filter of a multiple filter device can be used alone, the requirements of thefull flow rate for the tests, as stated in this British Standard, shall be met.
When one filter of a multiple filter device is tested separately, the air flow specified for a test shall bedivided by the number of filters through which the air flow is proportioned. lf the filters’ breathingresistances meet Formula (1), the filter may be tested as a single filter with a proportioned flow.BS 8468-3.2 pdf download.