BS N5:1992 download free

06-10-2021 comment

BS N5:1992 download free.Specification for Crew portable protective breathing equipment for use during aircraft emergencies.
1 Scope
BS N5 classifies and specifies the design, performance and testing requirements for portable protective breathing equipment for use by crew during specified emergency conditions on board an aircraft.
NOTE 1 The latest revision of an Aerospace Series standard is indicated by a prefixed number.
NOTE 2 The term ‘equipment” refers to portable protective breathing equipment or portable protective breathing equipment and its container.
2 Normative references
BS N5 incorporates, by reference, provisions from specific editions of other publications. These normative references are cited at the appropriate points in the text and the publications are listed on the inside back cover. Subsequent amendments to, or revisions of, any of these publications apply to this standard only when incorporated in it by updating or revision.
3 Definitions
For the purposes of this standard the following definitions apply.
any cabin attendant or member of the flight crew not engaged in primary operation of the aircraft
normal cabin altitude
the equivalent pressure altitude in the cabin not exceeding 10 000 feet (522.6 mm Hg)
an aircraft operating with passenger and freight areas on the main cabin deck
4 Classification
Portable protective breathing equipment conforming to this standard shall be classified according to its performance capability for use by a crew member during one of the emergency conditions at normal cabin altitude or on the ground shown in Table 1.
5 Design
5.1 General
5.1.1 The equipment shall be self-contained and incorporate a supply of breathable gas.
5.1.2 The equipment shall be easily fitted and removed without assistance.
5.1.3 The equipment shall operate when fitted at any time during the breathing cycle.
5.1.4 All classes of equipment shall be capable of being fitted and simply activated from the stowed condition by a trained person within 10 s.
5.1.5 To purge the equipment, an initial supply of breathable gas equivalent to one effective dead volume shall be provided within the initial 20 s of operation.
5.1.6 The equipment shall resist puncture and tearing.
5.2 Ergonomic
When correctly fitted in accordance with the manufacturer’s instructions the equipment shall perform as follows:
a) protect the head and neck of the user from dripping polymeric materials at 200 °C;
b) protect any adult without facial hair within the 5th female to 95th male percentile user population to the requirements specified in 6.1 to 6.5;
c) be compatible with the wearing of spectacles;
d) satisfy the vision requirements specified in 6.7;
e) allow intelligible two-way voice communication with or without the use of hand sets or megaphone as specified in 6.8:
f) not cause undue discomfort (see 7.3.1) during its period of use and shall leave both hands free:
g) not hinder the wearer to pass through an access of 460 mm X 460 mm (see 7.3.4).
5.3 Breathable gas
The supply of breathable gas shall conform to one of the following:
a) chemically generated oxygen conforming to
BS 2N2:1989:
b) gaseous breathing oxygen conforming to
BS 2N3:1990.
5.4 Hazard reduction
5.4.1 The equipment shall not create a hazard to the occupants or the aircraft under normal or fault conditions.
5.4.2 The equipment shall incorporate the following:
a) a means to prevent over-pressurization of the breathing circuit; the operation of this means shall not affect the integrity of the equipment;
b) rupture protection against over-temperature or over-pressurization of any pressurized containers, within the equipment, unless it can be shown that such conditions do not present a hazard.
5.5 Indication
5.5.1 The equipment shall incorporate a means to determine serviceability in the stowed position.
5.5.2 The absence, cessation after initiation, or expiry of the breathable gas supply shall be indicated to the user.
5.6 Materials
5.6.1 Any materials used in the construction of the equipment shall, where appropriate, conform to clause 4 of BS 3N 100:1985.
5.6.2 All materials used in the construction of the exposed surfaces of the unit and its case shall conform to 2.2 b) of CAA specification No.841]. In addition, the materials shall not be adversely affected by toxic gas and smoke.
5.6.3 The exposed portion of the unit shall conform to 7.4.
5.7 Environmental
The stowed equipment shall conform to 7.4.
6 Performance
6.1 Breathing resistance
When tested in accordance with 7.1.1, the breathing resistance shall not exceed ± 0.875 kPa at peak flow during inspiration or expiration.
6.2 Peak breathing flow
When tested at peak breathing flow in accordance with 7.1.1 for a period of 30 s, the equipment shall continue to operate.
6.3 Inhalation temperature
6.3.1 When tested in accordance with 7.1.1. the breathable gas temperature adjacent to the wearer shall not exceed 40 °C (wet bulb) or 67 °C (dry bulb) at 21 °C ambient temperature.
6.3.2 When tested in accordance with 7.1.1. the unit shall operate satisfactorily for a 2 mm exposure to an ambient temperature of 100 °C, and the breathable gas temperature in contact with the wearer shall not exceed 50 °C (wet bulb) or 90 °C (dry bulb).
6.4 Protection level (inward leakage) When tested in accordance with 7.2. the equipment shall protect the user’s eyes, nose and mouth against the surrounding atmosphere such that not more than 5 % leakage into the protected areas occurs during the duration given in 6.6.
6.5 Breathable gas
6.5.1 Purity
When tested in accordance with 7.2. the mean inspiratory levels of contaminants shall not exceed the following values:
a) Carbon dioxide
The CO9 concentration at mouth/nose shall not exceed 4 % at sea level, but a concentration increase to 5 °A at sea level for a period not exceeding 2 mm shall be permitted.
b) carbon monoxide
The levels of contaminants shall not exceed 50 ppm (time weighted average).
c) Chlorine
The levels of contaminants shall not exceed 1 ppm (time weighted average).
6.5.2 Oxygen level
When tested in accordance with 7.2. the minimum mean inspired oxygen level shall be not less than 130 mm Hg partial pressure.
NOTE 130 mm Hg oxygen partial pressure is equivalent to an altitude of 5 000 ft.
6.6 Protection duration
When tested in accordance with 7.2, the duration of protection provided by the equipment shall be as follows:
a) Class I equipment shall have a duration of 15 mm.
b) Class 2 equipment shall have a duration of 5 mm.
c) Class 3 equipment shall have a duration of 20 mm.
d) Class 4 equipment shall have a duration of 30 mm (Class 1 performance repeated).
6.7 Vision
6.7.1 General
When tested in accordance with 7.3.2. the equipment shall satisfy 6.7.1 and 6.7.2.
6.7.2 Optical qualities
The optical quality and light transmission shall not prevent a wearer from recognizing a standard aisle exit location sign in clear air during use.
6.7.3 Field of vision
The equipment shall provide a wearer with the following minimum field of view relative to the head:
a) horizontal meridian. 1200 (60° on each side of the centre line of view of the wearer);
b) vertical meridian. 80° (40° above and 40° below the centre line of view of the wearer).
6.8 Communication
When tested in accordance with 7.3.3. the user shall be able to communicate with another user or non-user of the same equipment at 4 m distance.
6.9 Fire and thermal resistance When tested in accordance with 7.3.5, the equipment shall withstand the following:
a) radiant heat flux levels
of 1.14 W/cm2 (1.0 BTU/sq ft/s) for 60 s;
NOTE A radiant heat source of sufficient size to expose the case and exposed parts of the unit to the stated heat flux should be used.
b) a 1 000 °C flame for 5 s without material penetration;
c) dripping polymeric materials at 200 °C, using burning polypropylene rod(s) and adjusting the height to give 200 °C contact temperature.
7 Testing
7.1 Lung simulator performance
7.1.1 The equipment shall he subjected to the lung simulator performance tests BS 4667-4:1989 and BS 4667-5:1990 as specified in Table 2. The tests shall be performed at sea level conditions (760 mm Hg) and at an equivalent pressure altitude to 10 000 feet (522.6 mm Hg). Field of vision
The field of vision shall be measured in accordance with Annex A.
7.3.3 Communication
It shall be demonstrated that intelligible communication, between two wearers, is possible by:
a) use of handsets (telephones);
b) use of megaphone by wearers standing 4 m apart;
c) accurate response of one wearer to five commands shouted by the other wearer standing 4 rn away in background noise conditions of 40 dB.
7.3.4 Access
A wearer shall be able to crawl through a vertically mounted square frame of 460 mm X 460 mm internal dimensions.
7.3.5 Fire and thermal resistance Radiant heat test
The radiant heat requirements of 6.9 a) shall be tested in accordance with the procedures outlined in BS 476-13:1987, or equivalent. Polymeric material drip test
The requirements of 6.9 c) shall be demonstrated by igniting a pure polypropylene rod (3 mm to 6 mm diameter), held horizontally, and allowing the drips to impinge on all external surfaces and material interfaces. The drop height shall be adjusted so that the drop contact temperature is at least 200 °C. Flame exposure test
The flame exposure requirements of 6.9 b) shall be tested in accordance with the procedures outlined in BS 4667-5:1990. or equivalent. Testing shall be performed upon a functioning equipment containing working levels of oxygen. The equipment shall be functional after the test.

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