Siebe Gorman Minox

Minox Oxygen Breathing Apparatus Specifications

The Minox is a one-hour minimum duration, closed-circuit oxygen breathing apparatus developed by Siebe Gorman (p. 5). Its key innovation is a compact, efficient flow control unit that replaces the conventional reducing valve, simplifying initial check procedures (pp. 5-6). The apparatus is back-worn, housed in a tough moulded glass fibre case, and can be fitted with either a wide vision face mask or a mouthpiece (p. 5). 

Technical Data 

• Weight (fully charged): 23.5 lb (10.6 kg) (p. 5)
• Duration: 1 hour rated + 25% reserve (p. 5)
• Cylinder Capacity: 12.7 cu ft (360 litres) at 2,500 psig (170 atm) (p. 5)
• Oxygen Flow Rate: 6.0–8.0 litres/min initially at 2,500 psig, reducing to 2 litres/min after 60 minutes of use as pressure falls (pp. 5-6)
• Absorbent: 2.5 lb (1.1 kg) of 8-12 mesh Protosorb (granulated soda lime) for absorption (pp. 5-6)
• Coolant: Two 1 lb (0.45 kg) packs of sodium phosphate for cooling the inspired oxygen (pp. 5-6)
• Inspired Air Temperature: Rising to a maximum of 37°C after 1 hour (p. 5) 

Design Features 

• Flow Control Unit: A novel unit without moving parts, factory sealed during manufacture, provides an initial high flow of oxygen to flush the circuit and supply the wearer’s demands (pp. 5-6).
• By-pass Valve: A hand-operated lever allows for an emergency oxygen flow in case of an incident (p. 6).
• Warning Whistle: A low-pressure warning whistle is connected to the pressure gauge adaptor (p. 6).
• Maintenance: Features such as ‘O’ ring seals and hand-tight connections facilitate ease of maintenance (p. 5).
• Desiccant: A sealed capsule containing silica gel ensures oxygen dryness, enabling use in temperatures as low as 16°C without freezing (p. 6).
• Harness: A blue Terylene harness allows for rapid adjustment and secures the apparatus to the wearer’s back (p. 7).
• Pressure Gauge: Calibrated in atmospheres and minutes, featuring a red portion indicating the reserve (p. 6).

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