Puncture Resistant Midsoles In Work Boots & Safety Shoes

Treading in a nail or on glass at work - will a steel midsole protect my feet better than kevlar?

How many workmates do you know that have stood on a nail or something sharp? 

If penetrating through the sole of your work boots you can rest assured, it’s a painful experience and at worst, it can deplete your sickies account if catching blood poisoning through a rusty nail or dirty pieces of broken glass leaving their “mark”. 

This is the main reason why a flexible, puncture-resistant midsole comes as a key criteria in any safety boot or work shoe. For example, anyone working around a tradie workshop, on a construction site, in a recycling plant, etc should ensure their footwear has either a steel or kevlar midsole.

The midsole can also be referred to as an 'insert plate' or 'protective insert plate' in technical terms for the bootmaker. There are primarily two types of puncture-resistant midsoles available, Steel (metal - not-so airport friendly work boot...) or Kevlar, woven material (non-metallic, airport-friendly safety boot).

The underlying question is obviously: What is better for my workplace and my personal safety?

How does a penetration resistant midsole work in safety boots?

A penetration resistant midsole covers (as per definition in the international safety standards) the entire foot.

Depending on the safety footwear manufacturer, it should be  lightweight and allow some sort of flexibility when crouching, i.e. offering comfort to users all day long. 

Steel midsoles mark the origin of penetration prevention in work boots and have been in use for many years.

 If selecting a boot with a steel midsole, most premium manufacturers of quality footwear are using stainless steel in the process as it will not corrode and break down over time.  - something to watch out for on cheaper footwear, which tends to use lower quality components. 

There is a degree of flexibility with a steel midsole and they protect the foot against the finest sharps and glass, including needles and broken blades of carpet knives.

Comparing non-metallic midsoles to steel midsoles there is one downside:

Flexibility: Metal usually does not bend as easily as the composite material. 

Kevlar or woven inserts are gaining more and more popularity. 

They usually consist of several layers of woven material which are bonded together under pressure through vulcanisation of different materials.  A key reason is that new kevlar-like materials are light and flexible, meaning they hardly add any weight to the boot by increasing the overall safety significantly. Secondly, the number of people traveling (fly in/fly out)  to work via airplane also has increased. The use of a non-metallic vs a metallic midsole in your composite toe caps ensures you do not need to take your boots off at the airport anymore. 

Downside?  If there is any downside, it is the fact they are more expensive than steel, and it's possible that a very fine point-like needle under intense pressure could penetrate between the weave of the fabric. That said, there is little (if any) evidence to corroborate this in real-life situations and it is likely that a robust rubber outsole would bend the needle tip before it struck the midsole material.

Are the  testing requirements for composite toe midsoles the same as for their steel midsole counterpart?

They are both tested using a sharp object as per definition by the safety standard. The tip of the sharp object must not penetrate through the test boot sole at all.

An additional testing requirement  is that the steel midsole is checked for corrosion resistance whereas the Kevlar midsole is tested for penetration, after being exposed to different climates and temperatures as well as the effects of acid, detergents, alkali, fuel & oil. 

How do I know my work boots have a midsole and keep me safe?

All safety boots and compliant work footwear need to indicate the midsole criteria on the label woven in the shoe or boot as follows:

The label inside the Shoe or boot shows the following letter number combination of either

• S1P

or

• S3 (as in the image)

So remember: The adequate choice of safety footwear goes along with the requirements and risks associated with the designated  work area. It is essential to ensure the physical and integral health of the worker.

If your work area presents a Hazard of sharp puncturing objects, request an S1P or S3 rate work boot of your preference which then includes the penetration resistant midsole.