A mesh upper works by giving sweat vapour an open path out of the shoe. Warm, humid air around your foot moves toward the cooler, drier air outside, and every step flexes the upper and pushes some of that air out through the mesh and the collar.
That is the whole mechanism, and it has limits. Mesh moves vapour, not puddles, it lets water in as easily as it lets air out, and the rest of the shoe decides as much as the upper does. Here is what the safety standard actually measures, and how to tell whether a shoe will breathe on a real shift.
What Breathable Actually Means In A Safety Shoe
In everyday language, breathable means "does not feel hot". In the safety standard it means something far more specific: a sample of the upper material has been measured for how much water vapour it lets through in a set time, and it has cleared a minimum figure.
The unit reads as milligrams of water vapour, per square centimetre of material, per hour. A square centimetre is roughly the size of a fingernail, so the upper minimum is less than a milligram of vapour through each fingernail sized patch every hour. That sounds tiny, but it is spread across the whole upper and runs for the whole shift.
Two things follow from this. First, "breathable" is a pass mark, not a ranking, so two shoes that both meet the standard can feel very different at hour eight. Second, the figure describes a material, not a finished shoe, which is a gap we will come back to.
If you want the ground floor first, we have a separate explainer on what a mesh upper is and how it is constructed. This article is about what happens once it is on your foot.
Where Your Feet Actually Sweat
Most people assume the sole of the foot is the sweatiest part. The research says otherwise, and it changes how you should think about mesh.
A study published in the International Journal of Clothing Science and Technology mapped sweating across the feet of 32 people, using two independent laboratory methods. Its findings are directly relevant to anyone choosing footwear:
- The top of the foot sweated substantially more than the sole. The dorsal surface, the part a mesh upper covers, is where most of the output came from.
- The highest local rates were at the inner ankle. The collar and heel counter area sits right over it.
- Sweating across the sole was uniform. No single hot spot, just a steady, even output across the whole plantar surface.
- Men produced more than twice the sweat of women at the same relative work rate, which is one reason two colleagues can report completely different experiences in the same shoe.
The researchers concluded that footwear should follow a body mapping principle, using different materials on different parts of the foot. That is exactly the logic of a mesh upper: put the most open material over the area producing the most vapour. It is also why the sole side of the shoe is handled so differently, as the next section shows.
Three Routes Moisture Takes Out Of A Shoe
Sweat does not leave a shoe by one route. It takes three, and a well designed shoe uses all of them.
How moisture leaves a safety shoe
Each route handles a different part of the foot and works at a different speed.
Through the upper
Out of the collar
Into the insole
The second route is the one people forget. Walking turns the shoe into a small bellows, and a study in Scientific Reports that tracked in shoe conditions found that bacterial growth on the skin rose with temperature and humidity inside the shoe, and fell as the ventilation rate went up. It was a small study, three men over twelve days, but the direction is clear: moving air matters as much as the material it moves through.
That has a practical consequence for workers who stand still. A picker walking the aisles all shift gets constant pumping. A worker at a fixed station gets very little, so the upper and the insole carry nearly all the load.
How The Standard Tests Breathability
EN ISO 20345 sets the requirement, and the companion standard ISO 20344 sets the method. The procedure is simple, and knowing it helps you read the result properly.
- The material is flexed first. Specimens are pre conditioned on a flexing machine, so the test reflects material that has already been bent the way a shoe bends, not a pristine sheet.
- A sample is sealed over a jar of desiccant. A disc of the upper material is fixed over the neck of a holder containing silica gel, which pulls moisture through the material.
- It runs in controlled air. The holders turn on a rotating table in a conditioned room at 23 C and 50 percent relative humidity, for a period of roughly seven to eight hours.
- The gain in weight is the answer. The holders are weighed before and after. The extra weight is water vapour that passed through the material, and that becomes the permeability figure.
- Absorption is measured too. A separate test records how much vapour the material soaks up, and the two figures are combined into a water vapour coefficient, which must reach 15 mg per cm² for the upper.
What the test does not doIt never tests the finished shoe. There is no foot, no sock, no toe cap, no walking and no sweat. It tells you the material can breathe. Whether the assembled shoe does depends on everything else built around it.
Every Layer Has To Breathe, Not Just The Mesh
Sweat does not meet the mesh first. It has to pass through the sock, then the lining, then any foam padding, and only then the outer mesh. The whole stack is only as open as its tightest layer, which is why the standard sets its own minimums for the inner layers too.
| Layer | What the standard requires | Why it matters |
|---|---|---|
| Upper | Permeability of at least 0.8 mg/cm²/h, and a coefficient of at least 15 mg/cm² | The outer exit for vapour from the top of the foot |
| Lining | Permeability of at least 2.0 mg/cm²/h, and a coefficient of at least 20 mg/cm² | Sits against the sock, so it must be two and a half times more open than the upper |
| Insole | Absorbs at least 70 mg/cm², then gives back at least 80 percent of it | Handles the sole, where the outsole blocks any exit below |
| Sock | Not covered by the standard | Often the tightest layer in the whole stack, and entirely your choice |
That last row is the one most people overlook. A thick cotton sock can hold moisture against the skin no matter how open the upper is. Wicking synthetic or wool blend socks move it outward so the rest of the stack can do its job.
The toe cap is the other fixed barrier. Aluminium, steel and composite caps do not pass vapour at all, so the mesh stretched over the front of the shoe cannot breathe through the cap beneath it. Designers accept this because the protection is not negotiable, and because the mapping research puts the heaviest sweat output higher up the foot, around the instep and ankle.
The 2022 Rule That Caught Out Heavy Overlays
Look closely at many modern safety trainers and the "mesh" upper is partly covered in welded plastic cages, printed films, rubber toe bumpers and logos. All of those are useful for durability and looks. None of them breathe. The 2022 edition of the standard started counting them.
How much of an upper may be non breathable
Share of the upper covered by non vapour permeable material, EN ISO 20345:2022.
This is one of the more useful changes in the current edition, and it gets very little attention. It means a heavily caged shoe has to earn its certification with a much more open mesh underneath. It also gives you a quick visual check in the shop: the more of the upper you can see through, the less work each remaining patch of mesh has to do. We covered the rest of the revision in our guide to what changed between the 2011 and 2022 editions.
What Mesh Cannot Do
The same openness that lets vapour out lets other things in. This is not a flaw in any particular shoe. It is simply physics, and it decides where a mesh upper belongs.
- It does not keep water out. An S1P upper is not tested for water penetration at all. The S2 class adds a test where the upper is flexed in water for 60 minutes and may let through no more than 0.2 g, which is why we set out the honest difference between S2 and S1P before anyone buys mesh for wet work.
- It does not stop liquids. Hot spills, cleaning chemicals and oils pass through open textile faster than through leather or coated materials.
- It does not resist sparks or hot surfaces. Synthetic mesh can be marked or melted by heat that leather would shrug off, and an outsole heat marking says nothing about the upper, as our breakdown of what the HRO marking does and does not cover explains.
- It does not keep fine dust out. Plaster, sawdust and grit can work through an open knit and collect inside the shoe.
- It does not dry you out when you stand still. Without the pumping effect of walking, mesh relies on slow diffusion alone.
Where A Mesh Upper Makes Sense And Where It Does Not
Put the physics together and the fit decision becomes fairly clear. Mesh earns its place where the main problem is heat and sweat on dry floors. It is the wrong upper where the main problem is water, heat or splashes from outside.
| A mesh upper tends to suit | Choose a different upper |
|---|---|
| Warehouse picking and packing on dry floors | Wet outdoor work, standing water, rain and mud |
| Delivery drivers and depot staff | Welding, grinding, hot cutting or foundry work |
| Indoor facilities and light maintenance | Regular chemical handling or wash down areas |
| Retail stockrooms and back of house | Heavy construction, groundworks and demolition |
| Indoor fit out and decorating, where S1P is accepted | Kitchens with frequent hot spills onto the foot |
Your employer's risk assessment always has the final word. If it calls for water resistance, a higher class or a specialist standard, that requirement outranks comfort. For a fuller side by side on durability, protection and feel, we compared how mesh and leather uppers compare overall in a separate guide.
How To Get The Most From A Breathable Shoe
A breathable upper is half the job. How you wear and rest the shoe decides the other half, and none of these steps cost anything.
- Wear wicking socks. Swap thick cotton for synthetic or wool blends that move moisture away from the skin, so the lining and upper have something to work with.
- Rotate two pairs if you can. The Royal College of Podiatry advises that shoes take 24 to 48 hours to dry out properly and recommends alternating pairs daily.
- Open the shoe up after a shift. Take the insoles out, loosen the laces and open the shoe fully, so the insole can release what it absorbed.
- Dry gently. For speed, the same guidance suggests a hairdryer on a cold setting rather than direct heat.
- Get the fit right. A shoe that grips the foot correctly flexes with you and pumps air on every step. A sloppy fit causes rubbing, and damp skin rubs more readily, which is how blisters start.
Moisture and friction work together. Damp skin is more prone to friction damage, and the Royal College of Podiatry notes that fungal infections such as athlete's foot thrive in the warm, dark and sweaty environment of feet inside shoes and trainers. A breathable upper reduces that environment, it does not remove it. We looked at the wider picture in what happens to your feet over a ten hour shift.
The Honest Verdict
Mesh uppers work, and the reasons are simple physics: an open path for vapour over the part of the foot that sweats most, plus the pumping action of every step. The standard sets a real floor for that performance, and the 2022 edition closed a loophole by counting non breathable overlays against the upper.
But breathability is a system, not a material. The sock, the lining, the insole, the toe cap, the fit and whether you are walking or standing all change the result, and the certificate only ever tested a flexed sample of fabric over a jar of silica gel. Judge a breathable shoe by the whole stack, and choose mesh for dry, warm, active work rather than for water, heat or splashes.
Xnexz PulseX and StrideX use a breathable mesh and microfiber upper intended to reduce heat build-up on dry indoor floors. They are S1P shoes, not water resistant, so they are not the right pick for wet outdoor work.
Frequently Asked Questions
How does a mesh upper make a safety shoe breathable?
It gives water vapour an open path out. Humid air around the foot moves toward drier air outside, and each step flexes the shoe and pushes some of that air out through the mesh and the collar. The insole absorbs sweat from the sole and releases it later.
Are mesh safety shoes waterproof?
No. The openness that lets vapour out also lets water in. S1P uppers are not tested for water penetration, while S2 adds a 60 minute flexing test in water. For wet work, look at S2, S3 or the newer S6 and S7 classes.
What does the safety standard require for breathability?
EN ISO 20345 requires the upper to have a water vapour permeability of at least 0.8 mg/cm²/h and a coefficient of at least 15 mg/cm². The lining must reach 2.0 and 20, and the insole must absorb at least 70 mg/cm² and release at least 80 percent of it.
Why do my feet still sweat in mesh safety shoes?
Because the upper is only one layer. Thick cotton socks, a tight lining, a large area of plastic overlays or standing still for long periods can all slow the process. The top of the foot also produces more sweat than the sole, so output can be high.
Does the toe cap stop the shoe breathing?
Over the toes, yes. Aluminium, steel and composite toe caps do not pass vapour, so the front of the shoe breathes less than the rest. Research suggests the heaviest sweat output sits higher up the foot, around the instep and inner ankle.
What changed about breathability in the 2022 standard?
It began counting non breathable materials on the upper. Up to 10 percent is accepted under the normal rule. Between 10 and 25 percent, the breathable parts must reach 2.0 mg/cm²/h. Above 25 percent, the upper fails.
How long do safety shoes take to dry out?
The Royal College of Podiatry advises that shoes take 24 to 48 hours to dry out properly, and recommends alternating pairs daily. Removing the insoles and loosening the laces after each shift helps.
Is mesh suitable for kitchen or hospitality work?
Sometimes, where S1P is accepted and hot spills onto the foot are rare. Where spills are frequent, a more closed and liquid resistant upper is the safer choice. Your employer's risk assessment should decide.
Breathable S1P For Dry, Busy Shifts
If your workplace accepts S1P and your day is spent moving on dry indoor floors, try Xnexz in a real shift. Then tell us honestly how the fit, comfort and breathability hold up, and what we should improve.
