This European Standard is applicable to operator seats used on industrial trucks as defined in ISO 5053:1987 irrespective of power supply, type of equipment, lifting mechanism and tyres. It also applies to seats for other trucks not covered by ISO 5053:1987, e. g. variable-reach trucks and lowlift order picking trucks. This European Standard specifies, in accordance with EN 30326-1, a laboratory method for measuring and evaluating the effectiveness of the seat suspension in reducing the vertical wholebody vibration transmitted to the operator of industrial trucks at frequencies between 1 Hz and 20 Hz. This European Standard defines the input spectral classes required for the following industrial trucks. Each class defines a group of machines having similar vibration characteristics: Platform trucks, trucks rider-controlled, etc. with wheel mean diameter below 200 mm and highload nonrubber solid tyres (category 1) 1) Reach trucks, articulated trucks, etc. with wheel mean diameter below 450 mm and high-load non-rubber solid tyres or cylindrical/conical base rubber solid tyres (category 2) 1) Straddle trucks, trucks with wheel mean diameter below 645 mm and rubber solid or pneumatic tyres (category 3) 1) Straddle trucks, trucks with wheel mean diameter between 645 mm and 900 mm and rubber solid or pneumatic tyres (category 4a) 1) Straddle trucks, trucks with wheel mean diameter between 900 mm and 1200 mm and rubber solid or pneumatic tyres (category 4b) 1) Trucks with wheel mean diameter between 1200 mm and 2000 mm and rubber solid or pneumatic tyres (category 5) 1) All-terrain trucks (category 6)1) This European Standard specifies performance criteria to be achieved by seats intended for each of the above-mentioned groups of machines. The tests and criteria defined in this European Standard are intended for operator seats used in industrial trucks of conventional design. NOTE Other tests may be appropriate for machines with design features that result in significantly different vibration characteristics. This European Standard is only concerned with the vertical component of whole-body vibration. Vibration which reaches the operator other than through his seat, for example that sensed by his feet on the platform or control pedals or by his hands on the steering-wheel, is not covered.