ISO 23328-1 Breathing system filters for anaesthetic and
respiratory use —Part 1: Salt test method to assess
filtration performance
Annex A
Conditioning of BSF
A.1 Principle
BSF are exposed to humidified air in a conditioning apparatus to
simulate a period of clinical use before they are tested for
filtration efficiency. The conditioning apparatus consists of a
humidity-generating patient model connected to a breathing
system with or without an inspiratory limb humidity generator. The
BSF can be positioned at various points in the breathing
system, to simulate clinical use or as recommended by
the manufacturer.
A.2 Test conditions
The ambient conditions during the conditioning shall be:
temperature: (23 ± 2) °C;
relative humidity: (60 ± 15) % RH;
pressure: (96 ± 10) kPa.
A.3 Apparatus
A.3.1 Inspiratory limb humidity generator [see Figure A.1 a)], to
increase the temperature and relative humidity of the inspired
air if required (see A.4).
A.3.2 Breathing system [see Figure A.1 b)], consisting of an
inspiratory limb, a Y-piece with a patient connection port,
and an expiratory limb, having one-way valves placed at the ends of
the breathing system limbs to ensure unidirectional flow
through the breathing system.
A.3.3 Humidity-generating patient model [see Figure A.1 c)].
The model shall consist of the following:
a) an insulated chamber, the internal temperature of which is
maintained at (37 ± 1) °C;
b) a heated water bath, maintained at (37 ± 1) °C, through which
air is bubbled in both directions;
c) a rigid reservoir containing a 2 l reservoir bag;
d) a reciprocating piston/bellows pump.
A.4 Positioning of BSF
A.4.1 General
The positioning of BSF for conditioning shall be as shown in Figure
A.1 and as described in A.4.2 and A.4.3
A.4.2 With the inspiratory limb humidity generator in place in the
breathing system
A.4.2.1 To simulate use in a circle breathing system with a carbon
dioxide absorber, set the mean temperature at the inlet to the
Y-piece to (26 ± 1) °C and the relative humidity to > 90 % RH
and place the BSF at position A.
A.4.2.2 To simulate use with a hot water humidifier, set the mean
temperature at the inlet to the Y-piece to (38 ± 1) °C and the
relative humidity to > 90 % RH and place the BSF at position B.
A.4.3 With the inspiratory limb humidity generator removed from the
breathing system
A.4.3.1 To simulate use in a non-rebreathing system, place the BSF
at position A.
A.4.3.2 To simulate use in the expiratory limb of a breathing
system, place the BSF at position C.
A.5 Procedure
A.5.1 Set up the apparatus and operate the humidity-generating
patient model, ensuring that the water bath temperature has
stabilized at (37 ± 1) °C. For the conditioning requirements
specified in A.4.2, operate the inspiratory limb humidity
generator until the temperature and humidity measured at position 1
of Figure A.1 have reached the specified values. Set the
patient model parameters according to the intended use of the
BSF, as given in Table A.1.
A.5.2 Fit the BSF in the breathing system at the position required
to simulate its intended use, as given in A.4 and Figure A.1.
A.5.3 Operate the apparatus to condition the BSF for the maximum
period recommended by the manufacturer for clinical use, or
for (25 ± 1) h if this is not stated.
A.5.4 Within 5 min of the end of the conditioning period, remove
the conditioned BSF and test the BSF in accordance with Clause
3
Table A.1 — Patient model parameters for conditioning BSF
Key
1 position of temperature and humidity sensor for use with
inspiratory limb humidity generator
2 insulated enclosure
3 rigid reservoir
4 pump
A, B, C Positions of BSF for testing (see A.4)
NOTE Symbols are in accordance with ISO 8835-2.
Figure A.1 — Conditioning apparatus for BSF