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Interliners and hidden fabrics in furniture

Interliners are used in upholstery, but where do they fit in when it comes to the furniture flammability regulations?

From the earliest days of upholstery, interliners have been used to contain loose fillings such as feather and down, and more latterly polyester fibre or crumb foam. In addition, interliners can be used on loose cover suites to enable the outer cover to be removed for cleaning.

Over the years, as the fire properties of upholstered furniture have become an increasing concern, the concept of a fire barrier interliner has emerged, to prevent an accidental surface fire from igniting the interior filling of the furniture.

Interliner performance

As a general rule, all outer covers must be match resistant, passing the match test described in Schedule 5 Part 1 of the Furniture and Furnishings (Fire) (Safety) Regulations, published in the UK in 1988. The only exception to this is when the decorative outer cover is made from certain fibres (at least 75 per cent of its weight must be made from cotton, viscose, modal, flax, silk or wool, either alone or in combination) and cannot meet the match ignition criteria specified in the regulations. In this case, a specialised, fire-resistant interliner (often called a 'Schedule 3 interliner') can be used between the outer cover and the interior or filling. This fire-resistant interliner must pass the test specified in Schedule 3 of the regulations. In all cases, irrespective of whether a match-resistant cover or an interliner is used, the foam or other filling must pass the relevant ignitability test. There are no exceptions to this.

Whenever an interliner has been incorporated to allow the use of non match-resistant covers, it is important that this is reflected in the wording on the permanent label. The triangular, red-bordered swing tag stating ‘meets the 1988 safety regulations by inclusion of a fire resistant interliner’ must be used (see figure 1).

Figure 1: The label cited in the UK regulations suitable for non-match resistant covers and furniture fitted with a compliant Schedule 3 interliner.

Because the word ‘interliner’ and its functions can be misinterpreted, the requirements of the UK regulations are often misunderstood. A common mistake made by manufacturers is to assume that the use of a Schedule 3 interliner allows the use of non-compliant foams and other fillings – this is not the case.

Untreated covers

In 1988, the cover supply industry was concerned that fabrics were not readily treatable to achieve the required match resistance or that the treatment would ruin the handle of the fabric and/or make it unusable. As a result, the 1988 legislation provided a concession which may allow certain fabrics to be used untreated, but only with the use of a suitable fire-resistant barrier interliner. The interliner for use with such covers is required to meet the demanding requirements of Schedule 3 of the regulations. The Schedule 3 test uses the severe ‘Ignition Source 5’, and the interliner fabric is tested over a highly ignitable non-fire-retardant standard polyurethane foam after the interliner has been water soaked and dried (see box 1). A fabric which in its untreated form passes the cigarette test (as many cotton fabrics do) is acceptable as a cover if used with a fire barrier interliner underneath.

Box 1: Main points concerning the requirements for fire-resistant barrier interliners

Interliner

  • designed to protect the filling
  • tested for fire resistance after a water soak and line drying
  • tested to Schedule 3 using an ignition source 5
  • tested over a specified non-fire retardant foam filling.

The Furniture and Furnishings (Fire) (Safety) Regulations require domestic upholstery (that is, a composite of a cover and a filling) to be cigarette-resistant. This requirement still stands regardless of whether or not an interliner has been used on the furniture.

Invisible parts

Another common misconception surrounding interliners is that they must meet the ‘hidden fabrics’ requirements of the regulations. There are no requirements in the regulations for ‘hidden fabrics’. This is a common misunderstanding of the requirements for ‘invisible parts of the cover’. The regulations give specific requirements for covers (not fabrics) and fillings. Interliners are neither, so with the specific exception of the Schedule 3 interliner application, there is no requirement for interliners or indeed for any other fabrics used within the structure of the item of furniture (such as flaps, ties, and flies).

Invisible covers

An invisible cover is part of the exterior surface of a piece of furniture, that is obscured during normal use but can be revealed by removing a loose cushion or turning the item over (see main photograph). The regulations are specific in naming the following areas as being the only invisible parts of the cover:

All other areas of cover are specifically designated as ‘visible’.

The invisible parts of the cover are required to pass Schedule 5 Part 3 and Schedule 4 Part 2 of the regulations, which are less severe in that they are tested in combination with fire-resistant foam (which meets Schedule Part 1 of the regulations) and are not subject to water soaking.

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