Product Safety of Footwear
Footwear is one of the most used types of consumer products which act as much more than a simple fashion statement. Footwear items are designed for a whole range of end users with their durability and safety being important features. Composed of a large number of components, footwear has many modes for potential failure which represent a safety risk to the user. In the same way that tires on a vehicle are the only points of contact with the road and therefore are critical in avoiding accidents, footwear is a consumer’s point of contact with the ground and is similarly critical.
Feigning Ignorance is Not a Solution
There are a large number of product tests which can be undertaken to assess the durability and safety of footwear. In addition to the diverse range of restricted substance requirements due to the many different material types used, footwear physical testing can be segmented into those which directly represent durability and those which are safety critical.
Product failures related to safety aspects can represent some of the more serious and potentially damaging issues to both the consumer and the retailer. For the retailer, the cost of compensation is likely to be much less than the probable loss from negative brand exposure. Whilst there are a number of safety related issues which must be considered, footwear that has been correctly manufactured and tested prior to retail is unlikely to cause consumer injury.
Footwear Safety Critical Characteristics
How a shoe interacts with both the foot and the floor allows an assessment of those aspects which are most critical for safety. For the contact aspects between footwear and the floor the main characteristics to assess are the soles and heels. These two parts of the shoe interact very differently during use and are exposed to different types of forces during impact. Furthermore, each user has a unique walking profile and footwear must be able to withstand all of these variables.
In addition to the correct footwear fit, the method of attachment such as zippers, buckles, straps and laces are important in ensuring that the foot remains firmly fixed in to the shoe. Any slippage of the foot within the shoe or breakage of, for example, functional straps may cause the wearer to slip or fall with resultant injury.
Footwear Contact Safety Criteria
Contact between the shoe and the floor is predominantly due to the sole and heel. For both components, it is critical to ensure that they are both securely attached to the footwear and that they offer sufficient interaction with the floor to prevent slippage. The assessment of footwear to these two fundamental criteria is effected through testing slip resistance and strength of heel attachments.
The grip between the sole and the floor is arguably the most important characteristic of a shoe and one that should be assessed on all footwear products. This can be done under controlled conditions within a laboratory and the resistance to slip can be assessed both under dry and wet conditions. Footwear items that fail known criteria will offer significant safety risks and should not be sold.
Most footwear items have some form of heel whose detachment during use can lead to wearer injury. In particular for larger heels, such as ladies high heels, the stresses during wear are significant and appropriate construction techniques must be followed to ensure sufficient strength. Testing of heels is undertaken using a number of techniques including assessment of heel detachment strength, heel impact and heel fatigue.
Footwear Attachment Safety Criteria
There are many types of footwear designs, all of which use different methods to ensure that the foot is appropriately held in place. Most footwear items use some form of fasteners such as laces, zippers, hook and loop fasteners, functional straps and buckles, etc. and any sudden loss of performance can lead to wearer injury. During footwear assessment and testing, both the strength of the attachment of these fasteners to the shoe and the intrinsic product strength are determined. In addition to their initial performance, it is necessary to simulate wearer use and ensure that the performance is not reduced over time.
Most footwear products feature seams and stitch lines which may fail during use. The thread type and stitch density are important criteria in functional stitches and should be assessed as a safety feature. Furthermore, ensuring correct construction, for example by using reinforcement techniques, can further increase product performance.
A popular method of fastening is to use zippers as these can be simple and quick to use. Zippers can be assessed as a component to ascertain whether they have sufficient strength to be used as a shoe fastener and whether they are positioned correctly.
Hook And Loop Fasteners
These are convenient forms of fasteners and have become popular particularly for children’s shoes. These systems work by hooks on one face becoming entangled with the loops on the other. After repeated use the attachment strength can be significantly reduced and can easily fail causing the shoe to become loose and therefore unstable for the wearer. Appropriate testing should be undertaken to ensure that both initial and repeated use strength remains sufficient.
The safety performance of general footwear is critical in offering the consumer the best protection against injury during normal use. Footwear is constructed using many different components and methods. It is necessary to assess footwear as finished products to determine if they are sufficiently stable to withstand the stresses of wear. Fortunately, techniques are available to test their performance to the principle safety risks.
Find more information on SGS Services for the Textile & Footwear Industry, please visit SGS Softlines and Accessories website.
For further information, please contact:
Karen E. Kyllo, Ph.D.
Deputy Vice President, Global Softlines
SGS North America Inc.
t: +1 973 461 7934
Andrew Hudson, Ph.D.
Global Technical Manager (Leather and
Footwear), Global Softlines
SGS United Kingdom Limited
t: +44 7841 566777