BS 8547:2016 pdf download.Respiratory equipment – Breathing gas demand regulator used for diving to depths greater than 50 metres – Requirements and test methods.
3.4 dive/pre-dive control switch on the demand regulator that in the pre-dive position prevents free-flow when not connected to the respiratory tract [SOURCE: BS EN 250:2014, 3.26] 3.5 high pressure pressure inside the cylinder(s) and between the cylinder(s) and any pressure reducer [SOURCE: BS EN 250:2014, 3.2] 3.6 medium pressure pressure between the pressure reducer and the demand valve [SOURCE: BS EN 250:2014, 3.3] 3.7 rated working pressure maximum working pressure of the respective components [SOURCE: BS EN 250:2014, 3.4] 3.8 reference pressure equilibrium pressure which exists in the face piece when there is no respiratory flow at the end of exhalation [SOURCE: BS EN 250:2014, 3.5] 3.9 respiratory minute volume (RMV) product of the tidal volume and breathing frequency measured in litres per minute [SOURCE: BS EN 250:2014, 3.10] 3.10 respiratory pressure differential pressure in the face piece relative to the reference pressure measured during inhalation and exhalation [SOURCE: BS EN 250:2014, 3.6] 3.11 work of breathing (WOB) external work expended during one breath divided by the tidal volume of that breath, measured in Joule per litre NOTE 1 This is equivalent to volume average respiratory pressure (kPa). This WOB is, in general, proportional to the area bounded by a pressure volume diagram. Work associated with positive pressures during inhalation does not count towards the total WOB. [SOURCE: BS EN 250:2014, 3.12, modified] NOTE 2 This is specific work, i.e. the work undertaken in ventilating one litre of gas.
4.2 Dive/pre-dive control If the demand regulator is fitted with a separate dive/pre-dive control, this shall be a two-position switch. If this is a rotational control, the rotation shall not be greater than 180°. The pre-dive setting shall be clearly defined and shall be marked accordingly. Demand regulators which incorporate a dive/pre-dive control shall be tested with the control set to dive position. 4.3 Demand regulator performance 4.3.1 Breathing performance The breathing performance shall be determined at simulated respiratory minute volume (RMV) up to 75 L·min −1 ambient temperature and pressure (ATP). The performance shall be determined with air at an ambient pressure of 6.0 bar and at the maximum pressure specified by the manufacturer using a gas mixture containing helium and greater than 2% oxygen with a density at that pressure of 7.66 g·L −1 . NOTE See Annex A for further information on gas density and gas mixtures. 4.3.2 Work of breathing and respiratory pressure The WOB at the maximum and minimum sensitivity (measured in J·L −1 ) shall not be greater than a value of: WOB = 0.5 + 0.03 × RMV The positive WOB during inhalation shall not be greater than 0.3 J·L −1 . The peak respiratory pressure during inhalation and exhalation shall be within the range of ±25 mbar. Pressure spikes (during inhalation) with no measurable positive WOB shall not be greater than 10 mbar. Pressure peaks (during inhalation) with measurable positive WOB shall not be greater than 5 mbar.BS 8547 pdf download.