BS EN 149:1992 download free.Specification for Filtering half masks to protect against particles.
Introduction
A given respiratory protective device can only be approved when the individual components satisfy the requirements of the test specification which may be a complete standard or part of a standard, and practical performance tests have been carried out on complete apparatus where specified in the appropriate standard. If for any reason a complete apparatus is not tested then simulation of the apparatus is permitted provided the respiratory characteristics and weight distribution are similar to those of the complete apparatus.
1 Object and field of application
BS EN 149BS EN 149 specifies minimum requirements for filtering half masks as respiratory protective devices against particles except for escape purposes.
Laboratory and practical performance tests are included for the assessment of compliance with the requirements.
2 References
EN 136:1989, Respiratory protective devices; Full face masks: Requirements, testing, marking.
EN 140:1989, Respiratory protective devices; Half masks and quarter masks; Requirements, testing, ,narking.
EN 143, Respiratory protective devices: Particle filters; Requirements, testing, marking.
3 Definition and description
A filtering half mask is one which covers the nose and mouth and possibly the chin and
a) consists entirely or substantially of filter material or,
b) comprises a facepiece in which the main filter(s) form an inseparable part of the device and where the prefilter may be replaceable.
It is intended to provide adequate sealing on the face of the wearer against the ambient atmosphere, when the skin is dry or moist and when the head is moved.
Air enters the filtering half mask and passes directly to the nose and mouth area of the facepiece or, via an inhalation valve(s) if fitted. The exhaled air flows through the filter material and/or an exhalation valve (if fitted) directly to the ambient atmosphere.
4.6 Flammability
The material used shall not present a danger for the wearer and shall not be of highly flammable nature.
When tested in accordance with 5.5 a filtering half mask shall not continue to burn after removal from the flame.
It is not required that the filtering half mask still has to be usable after the test.
4.7 Carbon dioxide content of the inhalation air
When tested in accordance with 5.6 the carbon dioxide content of the inhalation air (dead space) shall not exceed an average of 1,0 % (by volume).
4.8 Head harness
4.8.1 The head harness shall be designed so that the filtering half mask can be donned and removed easily.
Testing according to 5.3.
4.8.2 The head harness shall be adjustable or self-adjusting and shall be sufficiently robust to hold the filtering half mask firmly in position and be capable of maintaining total inward leakage requirements for the device.
Testing according to 5.3 and 5.4.
4.9 Field of vision
The field of vision is acceptable if determined so in practical performance tests in accordance with 5.3.
NOTE For comparative testing of the field of vision the method described in the European Standard for half masks EN 140 shall be used.
4.10 Inhalation and exhalation valves
4.10.1 Inhalation valve(s)
A filtering half mask may have one or more inhalation valve(s).
4.10.2 Exhalation valve(s)
A filtering half mask may have one or more exhalation valve(s), which shall function correctly in all orientations.
Testing according to 5.4.
4.10.2.1 If an exhalation valve is provided it shall he protected against dirt and mechanical damage and shall be shrouded or shall include any other device that may be necessary for the filtering half mask to comply with 4.4.
4.10.2.2 If an exhalation valve is provided it shall continue to operate correctly after a continuous exhalation flow of 300 1/mm over a period of 30 s. A total of 3 filtering half masks shall be tested; one as received and 2 temperature conditioned in accordance with 5.2.2.
5.4.2.2.3 Flame photometer
A flame photometer shall be used to measure the concentration of NaC1 inside the filtering half mask. Essential performance characteristics for a suitable instrument are:
1) It should be a flame photometer specifically
designed for the direct analysis of NaC1 aerosol.
2) It should be capable of measuring
concentrations of NaCI aerosol
between 15 mg/rn3 and 5 ng/m.
3) The total aerosol sample required by the
photometer should not be greater than 15 11mm.
4) The response time of the photometer, excluding the sampling system, should not be greater than 500 rns.
5) It is necessary to reduce the response to other elements, particularly carbon, the concentration of which will vary during the breathing cycle. This will be achieved by ensuring that the band pass width of the interference filter is no greater than 3 nm and that all necessary side-band filters are included.
5.4.2.2.4 Sample selector
A system is required which will switch the sample to the photometer only during the inhalation phase of the respiratory cycle. During the exhalation phase clean air shall be fed to the photometer. The essential elements of such a system are:
1) An electrically operated valve with a response time of the order of 100 ms. The valve should have the minimum possible dead space compatible with straight-through, unrestricted flow when open.
2) A pressure sensor which is capable of detecting a minimum pressure change of approx. 0,05 mbar and which can be connected to a probe inserted in the cavity of the filtering half mask. The sensor shall have an adjustable threshold and be capable of differential signalling when the threshold is crossed in either direction. The sensor shall work reliably when subjected to the accelerations produced by the head movements of the subject.
3) An interfacing system to actuate the valve in response to a signal from the pressure sensor.
4) A timing device to record the proportion of the total respiratory cycle during which sampling took place.
5.4.2.2.5 Sampling probe
The probe shall be fitted securely in an airtight manner to the filtering half mask as near as possible to the centre line of the filtering half mask. A multiple hole sampling probe is strongly recommended.
5.9.1.2 Test equipment
A scheme of a typical apparatus is given in Figure 10.
The double acting breathing
machine B (2 l]stroke, 15 cycles/mm) and the critical orifice 0 in conjunction maintain the flow rate through mixing chamber C and nozzle A essentially constant at 95 1/mm and 9,5 1/mm respectively throughout the sinusoidal breathing cycle, so ensuring consistent dust conditions within the chamber C.
For measuring pressure drop and setting up flow through nozzle A, valve X is set at CALIBRATE; during these operations the breathing machine is switched off. For testing the valve is set at TEST. For determining the quantity of dust which shall be introduced into the hopper H in order that 1,5 g be collected on the filtering half mask, valve Y is set at CALIBRATE: at this setting the flow rate during exhalation is zero.
5.9.1.3 Test conditions
The dust used for the clogging test shall be a coal dust prepared from Grimethorpe Washed Singles (upper seams), N.C.B. Coal Rank Code 502, volatile matter 35 %, ground by ball mill and graded by sieving, the portion which passes
a 240 mesh (63 micrometer aperture) sieve being used for the test.
5.9.1.4 Test procedure
The test apparatus shall be set up by connecting a weighed filtering half mask into the air circuit at the top of chamber C. Valve X shall be set to CALIBRATE and air shall be drawn through the filtering half mask at 95 11mm; valve E shall be adjusted until the flow through the
nozzle A is 9.5 1/mm. Valve X shall then be set to TEST and valve Y to CALIBRATE, a known weight of dust shall be fed into the hopper H and dispersed into the chamber. After dispersal, the filtering half mask shall be re-weighed. A number of filtering half masks shall be exposed until the weight of dust which shall be introduced into the hopper to give a 1,5 g collection is determined.
Connect the filtering half mask into the chamber. Valve Y shall be set to TEST, the previously determined weight of dust shall be introduced into the hopper H and after allowing the filtering half mask to reach equilibrium the dust shall be dispersed into chamber C. After dispersal valve X shall be set to CALIBRATE arid the breathing machine turned off. The pressure drop across the filtering half mask at 95 11mm shall be read off manometer M.
Repeat the test on the other two samples and report the 3 recorded pressure drops.