Seating can be tested in several ways. This article describes the assessment of physical aspects – strength, durability, stability and ergonomics – rather than such characteristics as fire resistance and the durability of upholstered parts. The furniture industry distinguishes between 'domestic' seating and 'non-domestic' seating. Non-domestic seating is often referred to as 'contract' seating.
Testing of seating may involve any or all of the following tests: static load, impact load or durability. In a typical static load test, a specified load is applied to the horizontal seat part and/or the vertical backrest part for a short period – perhaps ten seconds. In the case of outdoor seating, there is also an extra final static load application of 30 minutes. The combination of loads is applied several times – typically ten times. If any part of the structure or frame breaks, splits or becomes deformed, the seating fails the test. Failures are not always dramatic, and careful inspection may be required to reveal cracks, for example.
In an impact load test, a falling weight is allowed to strike the seating. The mass of the falling weight is specified, as is the distance through which the weight falls. As a variant of this impact test, a sideways impact may be called for, which uses a pendulum arrangement.
Arm rest and/or back rest
In durability tests, specified loads are applied to the seat and back rest in a cyclic fashion. In the 'seat and back durability test', the loads are applied to simulate a person sitting down on seating and then getting up out of it many thousands of times. The loads are not as large as those specified in the static tests. Another type of durability test is the 'seat front edge durability test'. In this case, alternating loads are applied on either side of the front edge of the seat. The exact positions where the loads are applied will vary according to the particular type of durability test. Structural components of the seating may develop faults in the durability tests that did not emerge in the simpler static tests. Automated systems are used to apply the loads (figure 1).
These systems are able to detect when a major structural failure has occurred and to stop the test. In the case of less dramatic failures, the automated systems will not stop, and the expert eye of a test engineer is needed to detect the problem.
In a stability test, the likelihood of seating tipping over in use is assessed. In separate variants of the tests, specified loads are applied at specified points on the seat, arms (if present) and the backrest. If the seating overturns forwards, sideways or rearwards, it has failed the test.
Most standards for seating include some requirements to ensure that in normal use the seating will not cause injury to the user are a result of sharp edges, or 'squeeze points'. To avoid sharp edges, a minimum radius for edges may be specified. The definition of squeeze points is a difficult area, and, in many cases, the determination of any such danger is subjective. Whether or not a squeeze point exists requires very careful consideration of the design and construction of the seating. A squeeze point is a danger point on seating, and may be defined in a standard with reference to any parts which move relative to each other in normal use. A user may trap his finger in a squeeze point, or perhaps in other features. Whether or not the parts do move relative to each other in normal use is not always easy to decide. Another safety requirement may be that ends of hollow components (such as tubes) are closed or capped to prevent fingers becoming trapped.
Which test standard to use?
In most cases, seating will be tested according to a particular national or international standard. The choice of which standard to use may sometimes seem daunting. In some cases, the end-user (or purchaser) of the seating may state what standard is required, and so the choice is made simple. On other occasions, the supplier or manufacturer of the seating may just want some evidence that the seating is 'fit for purpose' and 'safe', and so will need advice as to which standard is appropriate. In the case of novel designs, no existing standard may be appropriate. Therefore, an improvised test may need to be devised, perhaps adapting parts of the usual standards. Most standards are intended to show that seating is suitable for people weighing up to 110kg (17 stone), and so seating for 'bariatric' use (by very heavy people) will need to be tested using increased loads.
Some standards may include several levels of testing severity. This can mean, for instance, that seating for use in a library will be subjected to lower test loads and fewer fatigue cycles than seating for use in a prison. It should also be noted that often the choice of standard is not determined by the design of the seating, but instead by its intended use.
Table 1 highlights which standard applies. Note that outside Europe, USA ANSI/BIFMA standards may apply.
|Table 1: Seating testing standards|
|Type of seating||Applicable standards||Note|
|Office work chair||EN 1335* Parts 1,2,3,4
or BS 5459-2:2000+A2:2008
|An office work chair will rotate, have height adjustment and a back rest|
|Any other type of non-domestic seating**||EN 16139:2013||Includes sofas|
|Seating for outdoor use||EN 581-1:2006
|Includes camping chairs that fold and loungers|
|Ranked seating intended to be fixed to the floor||EN 12727:2000||Includes theatre seats|
|Seating for educational institutions||EN 1729-1:2015
|Chairs for pupils, not teachers|
|Domestic seating||EN 12520:2015||Includes sofas|
|* The four parts for EN 1335 are EN 1335-1:2000, EN 1335-2:2009, EN 1335-3:2009 and PR CEN/TR 1335-4:2009. Parts 1 and 4 are for dimensions only.
** Does not apply to office work chairs, chairs for educational establishments, outdoor seating or to linked seating.