So why is it dangerous for a passenger to have the phone switched ON and a ramp worker who has their phone ON.
Section 5.7.6 of the National Fire Protection Association (NFPA) 407 Standard for Aircraft Fuel Servicing 2001 Edition states that,
“Communications equipment used during aircraft fuel servicing operations within 3m (10ft) of the fueling equipment or the fill or vent points of aircraft fuel systems shall be intrinsically safe in accordance with UL 913, Standard for Intrinsically Safe Apparatus and Associated Apparatus for Use in Class I, II, and III Division I, Hazardous (Classified) Locations”.
Intrinsically safe can be described as
“electrical equipment that is incapable of releasing sufficient electrical or thermal energy under normal or abnormal operating conditions to cause ignition of a specific hazardous mixture and air”. These devices may be used in hazardous areas as they are designed with additional shielding and safeguards to reduce the risk almost completely.
However, normal consumer electronics and cellular telephones are not required to be certified as intrinsically safe and are not constructed or manufactured to this higher standard.
It is also interesting to note that in December 2003, the UK CAA published updated guidance related to passenger use of cellular telephones during aircraft refuelling:
1 USE OF CELLULAR TELEPHONES DURING AIRCRAFT REFUELLING
1.1 FODCOM 17/2003 highlighted CAA Paper 2003/3, which contains the full results of the research carried out to identify the susceptibility to interference of vulnerable avionic equipment from commonly used transmitting devices.
1.2 Following the publication of this CAA Paper, an enquiry has been received requesting clarification as to whether it is now acceptable for cellular telephones to be used on board aircraft during refuelling operations, contrary to the guidance given in CAP 74 – “Aircraft Fuelling: Fire Prevention and Safety Measures.”
1.3 The CAA is satisfied that fuel vapour ignition, due to the use of cellular telephones on the aircraft, is unlikely when passengers are onboard during fuelling operations. This position takes account of the energy levels of cellular telephone transmissions, absorption and attenuation of that energy within the cabin, and the separation that would exist between an onboard cellular telephone and an external fuel vapour source.
1.4 It is proposed to combine CAP 74 and CAP 434 – “Aviation Fuel at Aerodromes” into a new document, and to remove the text relating to the use of telephones by passengers on board during refuelling operations. Pending this revision, operators may relax their current restriction and permit the use of cellular telephones inside the aircraft during fuelling operations.
FODCOM 30/2003