Phase change, PCM
28°Cmelting point
- Best for
- Coastal and inland alike, because humidity does not affect it
- Run time
- Around 2.5 to 3 hours per charge
- Watch out for
- Weight, and you need a recharge system on site
Heat-Stress PPE
Cooling Vests, and Why 28 Degrees Beats Ice
Most people buying heat-stress PPE for the first time reach for the coldest thing available. It is the obvious move and it is the wrong one, because a pack at zero degrees makes the body worse at cooling itself.
This page explains what actually works on a UAE site, which technology suits the coast and which suits inland, and how the midday break fits into a recharge cycle. As a cooling vest supplier we deliver across all seven emirates from Ajman, from a minimum of 25 pieces.
The numbers that matter
Four figures behind a heat stress programme
28°C
Where work-vest PCM packs are formulated to melt
3 hrs
Typical run time from one charge, around 2.5 to 3
12:30
Outdoor work stops, 15 June to 15 September
25
Minimum order, pieces
Run time varies with ambient temperature, humidity and how hard the wearer is working. Treat three hours as a planning figure, not a guarantee.
The thing that surprises people
Why an ice pack makes heat stress worse, not better
Skin sits at roughly 33 to 35 degrees. Everything about how the body dumps heat depends on blood being able to carry it from the core out to that surface, where it can leave.
What cold does to blood flow
Put something at zero degrees against the skin and the body does what it is built to do when it detects cold. The vessels near the surface narrow. Blood flow to the skin drops. That is the correct response if you are losing heat and need to keep your core warm.
On a site in August it is exactly backwards. The worker needs blood moving to the surface so heat can leave, and the ice pack has just shut that route down. It feels wonderful for two minutes and then it is working against you.
Why 28 degrees is the number
Phase change packs for work vests are formulated to melt at around 28 degrees. That sits comfortably below skin temperature, so heat flows steadily from the body into the pack, and it sits far enough above freezing that the body never reads it as cold.
While the material is melting it holds that temperature instead of climbing with it. The vest does not slowly warm to body heat the way a gel pack does. It stays at 28 until the pack has fully melted, which is where the two and a half to three hours comes from.
The practical version. A 28 degree pack is not a weaker version of an ice pack. It is a different mechanism. Ice gives a large temperature difference for a short time and then triggers the response that stops the body cooling itself. A phase change pack gives a smaller difference that stays open for a full work cycle. For a crew doing three hours between breaks, the second one is the only one that lasts the shift.
Choosing the technology
Three types of cooling vest, and where each one belongs
These are not three price points of the same product. They work in completely different ways, and one of them fails badly in exactly the places most UAE sites are.
Evaporative
Watersoak and wear
- Best for
- Dry inland work, Al Ain and the interior
- Run time
- Several hours in dry air, far less in humidity
- Watch out for
- On the humid coast it becomes a wet, heavy garment that cools very little
Ice and gel pack
0°Cfrozen insert
- Best for
- Short, intense exposures with a rest straight after
- Run time
- Short. The packs warm quickly once melted
- Watch out for
- The vasoconstriction problem above, plus condensation inside the garment
Humidity is why the coast and the interior need different answers
An evaporative vest cools because water leaves it as vapour. That needs somewhere for the vapour to go, which means dry air.
The coastal strip through Dubai, Sharjah and Abu Dhabi runs humid through the summer. In that air an evaporative vest barely evaporates. It stays wet, it gets heavier, and the cooling you paid for does not arrive. Inland the same vest performs well. If your sites span both, one product is the wrong answer for one of them.
Weight is a real cost, so say it out loud
A PCM vest with a full set of packs carries weight, and carrying weight generates heat. A vest that is too heavy for the task can hand back some of what it gives.
That matters most for work already involving climbing, lifting or long walking. For a static or semi-static role it is a non-issue. Any cooling vest supplier who tells you weight does not matter has not worn one for a shift.
Placeholder. List the vest types, PCM melting points, pack counts and size range actually held in stock here, or delete this block. Nothing that cannot be evidenced should be published.
The rule this fits into
The midday break is your recharge window
Outdoor work in direct sunlight is prohibited from 12:30pm to 3:00pm, every day from 15 June to 15 September. Employers must provide shaded rest areas, cooling equipment, sufficient drinking water with approved rehydration salts, and first aid kits. Cooling equipment is written into that obligation rather than being optional.
| Time | What is happening | What the vests should be doing |
|---|---|---|
| Start of shift | Crew goes out with a fresh charge | First set in the vests, second set already charging |
| Around 12:00 | First set is reaching the end of its cycle | Nothing. It has done its job and the break is next |
| 12:30 to 3:00 | Work stops. Shade, water, salts, rest | First set goes into the charger. Crew rests without a vest |
| 3:01 onwards | Back out, close to the hottest part of the day | Second set goes on, fully charged |
Scroll the table sideways on a phone.
Two things fall out of that table. The first is that you need two sets of packs per vest, not one, or the afternoon runs uncharged. The second is less obvious and more important: the break ends at three o'clock, and three o'clock in August is usually hotter than noon, because ground and structures have been absorbing heat all morning. The crew walks back out into the peak. That afternoon stretch is what the second set is for, and it is covered in more detail in our piece on the MOHRE midday break.
If you are reviewing heat stress across a whole crew rather than one role, the same questions apply to the construction uniforms worn underneath. Cooling added on top of the wrong garment is the most expensive way to solve this.
The rest of the kit
Heat stress is not solved by a vest alone
A heat stress programme is five or six small things done together. Buy only the vest and the programme has a hole in it.
- Sun hoods and neck shades. Look for a stated UPF rating rather than a claim about being sun protective. The neck and ears take more direct sun than anywhere else on a site and they are the places nobody covers.
- Rehydration salts. Water alone does not replace what is lost in sweat. The rule names approved rehydration supplements specifically, which is a clue about how seriously it is taken.
- Cooling towels. Cheap, effective for a break, useless under a coverall. Good for the shaded rest area, not for the work.
- The base layer underneath. A cooling vest over a heavy, non-breathing coverall is fighting its own garment. Get the industrial coverall specification right first, then add cooling, not the other way around.
- Shade and airflow at the rest point. Shade alone in still air does far less than shade with a fan. The rule asks for cooling equipment at the worksite, and a fan in the rest area is the cheapest version of that.
A vest buys a crew roughly three hours at a time. Everything in these two columns is what makes those three hours hold, and a PPE supplier worth dealing with will raise all of it before quoting a vest on its own.
Branding and fit
Logos, sizing and how a vest should sit
A cooling vest carries a logo easily, because unlike a helmet or a boot there is no certification to disturb. Print is usually better than embroidery here, since the shell is often a light synthetic and a dense stitch field distorts it.
Fit is the part that decides whether the vest works. The packs have to sit against the torso, because a gap between the pack and the body is an insulating layer of air doing the opposite of what you want. Too loose and it cools nothing. Too tight over a coverall and nobody wears it past the first hour.
Order one size up if it goes over a coverall, and specify adjustable side straps rather than a fixed body. Most vests in a mixed crew end up on different people across a project, and adjustable sizing is what makes that possible.
Printing runs in house in Ajman, so branding does not add a separate lead time to the order.
Before you order
When a cooling vest is the wrong purchase
A vest manages heat load on a worker. It does not fix a schedule, a fabric or a site layout, and buying one to avoid fixing those is expensive.
- The coverall is the problem. If the crew is in a heavy, non-breathing garment, fix that first. A cooling vest over the wrong base layer is paying twice for one problem.
- There is no recharge system. Without a cooler, a freezer or cold water on site, PCM packs are single use and the programme collapses in week two. Budget the charging, not just the vests.
- Flame resistant work. A standard cooling vest is a synthetic garment and has no place on hot works. If the crew needs FR, the vest has to be specified for it, and most are not.
- The task is climbing or lifting all day. Added weight on that work can cancel the benefit. Look at shade, rotation and scheduling first.
- It is being bought instead of shade and water. Those are the legal minimum and they are not optional. A vest is what you add once they are in place.
Ordering
Four things to tell us, and the quote comes back today
Where the site is
Coastal or inland. It decides whether evaporative is even on the table.
What the work involves
Static, walking, climbing or lifting. Weight matters more on some than others.
Your recharge setup
Cooler, freezer or cold water. If there is none, say so and we will plan around it.
Quantity and base layer
Minimum 25 pieces, and tell us what goes underneath so sizing works.
Questions
What site managers ask a cooling vest supplier
Why are cooling vest packs 28 degrees and not frozen?
Because the body responds to cold by narrowing the blood vessels near the skin, which reduces blood flow to the surface and therefore reduces the amount of heat it can shed. An ice pack at zero degrees triggers that response, so it feels excellent for a couple of minutes and then works against the wearer. A pack formulated to melt at around 28 degrees sits below skin temperature of roughly 33 to 35 degrees, so heat keeps flowing out of the body, and it holds that temperature for the whole time it is melting rather than warming up gradually.
How long does a cooling vest last on one charge?
Around two and a half to three hours for a phase change vest, varying with ambient temperature, humidity and workload. Treat three hours as a planning figure rather than a guarantee. You need two sets of packs per vest so one set can be recharging during the midday break while the other covers the afternoon.
Do evaporative cooling vests work in Dubai?
Less well than most buyers expect. An evaporative vest cools as water leaves it as vapour, and that needs dry air. The coastal strip through Dubai, Sharjah and Abu Dhabi is humid through the summer, so the water does not evaporate properly and the vest becomes heavy rather than cool. Inland, in drier air, the same product performs well. Phase change vests are unaffected by humidity, which is why they suit sites that span both.
Does the UAE midday break require employers to provide cooling?
Outdoor work in direct sunlight is prohibited from 12:30pm to 3:00pm between 15 June and 15 September, and employers must provide shaded rest areas, appropriate cooling equipment at the worksite, sufficient drinking water with approved rehydration salts, and first aid kits. Cooling equipment is part of the obligation rather than an optional extra, though the rule does not specify a particular product.
Can a cooling vest be worn over a coverall?
Yes, and it usually is, but order one size up and specify adjustable side straps. The packs need to sit against the torso, because an air gap between the pack and the body acts as insulation and cancels the effect. If the coverall underneath is heavy and non-breathing, fix that specification first, because a cooling vest over the wrong base layer means paying twice to solve one problem.
Tell us the site and the shift, not just the quantity
Coastal or inland, what the crew actually does, and whether there is a way to recharge packs on site. Those three answers decide the product, and they are the questions a PPE supplier should be asking you first. Minimum order is 25 pieces and we are a working day away from any emirate.