ERGONOMICS UNIT

Date 06 June 2007

Ref 0107/HUMA/01/GS

Reported by Gina Sands

FIRA International LtdMaxwell RoadStevenage SG1 2EW

AN ASSESSMENT OF

Liberty pedestal armchair

Manufactured by

Humanscale

for compliance with BS EN 1335: Part 1 (2000)

0107/HUMA/01/GS

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TYPE A TYPE CMin Max Min Max Min Max Measurement Comments

a Seat height AdjustableMin Range

400120

510 420100

510 42080

480 400-508108

PASS

b Seat depth non-adjustableadjustableadjustment range

NO 40050

NO 420

380 40050

440 420

380 400

435-485

50c Depth of seat pad 380 380 380 510 PASSd Seat width 400 400 400 525 PASSe Inclination of seat

surfaceNon-adjustableadjustableadjustment range

NO-2

6

NO-7

-2-2

-7-7

-2-2

-7-7

-2.5 to –5

2.5

PASS

f Height of the back supporting point ‘S’ Above seat pad

Non-adjustableadjustableadjustment range

NO17050

NO 220

17017050

220220

170 220 120-215 PASS *As fixed height lumbar

g Height of the back pad

adjustablenon-adjustable

220260

220260 260 510 PASS

h Height of the upper edge of backrest

360 360 360 NA

i Back rest width 360 360 360 515 PASSk Horizontal radius of

the back rest400 400 400 400 on fabric PASS

l Back rest inclination Adjustment range 15 15 14 o pivot36 o tilt

PASS

n Length of armrest 200 200 200 200o Width of arm rest 40 40 40 40-80p Height of arm rest

above the seatNon-adjustableAdjustable

200200

250250

200 200

250 250

200200

250250

177-277 (to top surface)

PASS

q Distance from front of the arm rests to the front edge of the seat

100 100 100 100-145 PASS

r width between arms 460 510 460 510 460 480-515(fixed)

PASS

s Max offset of underframe

Non swivel Swivel castors

365415

365415

X+50380 PASS

t Stability dimensions 195 195 195 240 PASS

Table 1: Dimensional Analysis of Liberty pedestal armchair

TYPE B

SEAT

FAIL*

BACK REST

ARM REST

UNDERFRAME

≤≥

≥ ≤≥

≥ ≤≥

≥

≤≥

≥ ≤≥

≥≥ ≤

≥ ≥ ≥≥ ≥ ≥

≥ ° °

≤ °

° ≥ °

° ≤ °

° ≥ °

° ≤ °

° °

°

≤ ≥

≥ ≤ ≥

≥

≥ ≥

≥ ≥

≥

≥ ≥ ≥

≥ ≥ ≥ ≥ ≥ ≥

≥ ° ≥ °

≥ ≥ ≥ ≥ ≥ ≥

≤ ≥ ≤ ≥ ≤ ≥ ≥ ≥ ≥

≥

≤ ≤

≤ ≤

≥ ≥ ≥

0107/HUMA/01/GS

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The chair satisfied the dimensional requirements of BS EN 1335; Part 1 (2000) for Chair Type B, with the exception of the following points:

The seat pan of the Liberty chair slides in relation to the vertical position of the backrest. When measured on the median plane the effective seat depth of Liberty chair varies between 435 mm and 485 mm it also has a minimum adjustment range of 50 mm. The standard requires the seat depth to be below 420 mm. Thus, the Liberty chair would not technically comply with the required dimension in the standard. However, if the seat depth is measured 100 mm from the median plane, where the legs would be located, the minimum seat depth becomes 415 mm. Therefore the Liberty chair is considered to be truly seat depth adjustable and compiles with the requirements of the standard.

It is clear that the Liberty chair does not have a physically moving lumbar support. The back is shaped s that there is a lumbar point. Its height can be measured as described in the BS EN 1335 Part 1. This would appear to make the chair to have a fixed height lumbar support. In real life use the chair behaves as if it has a moving height adjustable lumbar support. During the user trials carried out at FIRA most users found that the chair provided sufficient support for their lower back and they felt no aches or pain. They found the chair to be very comfortable. Users varied from 1st percentile female to 96th percentile male. It is understood that the information Humanscale has about the experiences of users of Liberty chairs support this finding. This was supported by the separate investigation of users’ spine when standing, when sitting upright and reclined on the Liberty chair. It was found that the shape of spine of all users was in lordosis and in some cases it was better when sitting on the Liberty chair than standing. For further details refer to the Appendix of report ref 0107/HUMA/01E/GS. Consequently, it is considered that the Liberty chair would fulfil the lumbar support height adjustability requirements of the standard.

Therefore it is considered that the Liberty chair does comply with BS EN 1335: Part 1 (2000) for chair type B.

CONCLUSIONS

Dimension b: Seat depth

Dimension f: Height of Lumbar support Point S