Diary Of An ADI

A Driving Instructor's Blog

Neowise - I saw it!Yessss! The weather finally cleared up and I finally saw Comet Neowise with my own eyes.

This is just a handheld short-exposure shot, but it’s clearly there. And you can see it with the naked eye even in well-lit areas. It has a long visible tail.

If the weather looks good tomorrow, I might drive somewhere darker to try it with my tripod. And a longer exposure – trust me, with the naked eye, the tail is much more pronounced, but a snapshot doesn’t pick it up properly.

But the main thing is, I saw a comet! And a proper one with a tail.


ReadlyA couple of years ago I was having a clear out and I was amazed at the number of magazines I’d collected over the years. They were mainly my Classic Rock mags, and part of my decision to have a clear out was that I’d been getting more and more disillusioned with that particular publication.

At the time, I was on an annual subscription, but Planet Rock had just launched its own magazine and that did exactly what it said on the tin – it covered rock music. Classic Rock acquired a new editor, and she made it clear in her introductory piece what she was planning. Subsequently, any rock music they covered had to include at least half female acts – meaning it became obscure and far from ‘classic’, at best – and they also decided that (as just one example) Depeche Mode somehow ticked both the ‘classic’ and ‘rock’ boxes at the same time (actually, they decided twice in the space of just a couple of months with that one example). Then they did their ‘best 100 female artists of all time’ issue, and necessarily had to include non-rock genres to fill it out. That was it from me, and I cancelled my sub.

Before any feminists start frothing at the mouth over this, I go to see lots of female artists and bands with female members. I actually seek them out if I hear them on Planet Rock and like the sound. Like Samantha Fish, Haim, Paramore, Evanescence, Courtney Love, Joanne Shaw Taylor, The Lounge Kittens… I just don’t need any feminist magazine editors trying to filter out the men for me. And if you don’t like the fact that I don’t like that fact, click the back button and go somewhere else.

Planet Rock mag suits me fine, but when the lockdown came along, it also came with a lot of extra time for reading and finding tips on how to do stuff I wouldn’t have otherwise had time for. And going out to buy magazines wasn’t an option – even if it would have been of benefit with the ‘current’ issue on sale (you usually need a series of them).

A few years ago, as a result of my quest to find some authentic German food recipes, I came across a subscription service called Readly. It carries – and this is no exaggeration – thousands of UK titles. They’re all the ones you see on the newsstands (and many you don’t), from TV Times, OK!, Hello!, through all the photography and amateur DIY magazines, through to music and musicians (including Classic Rock). They cover specialist computer and technology subjects, gaming, weddings, cycling, fishing, horse riding, pets… everything (but no X-rated adult stuff). Including back issues, too, which multiplies the content by at least ten. And as I already implied, they have similar numbers of publications from Europe, Asia, and America. They’ve also recently started including newspapers, though it’s only The Independent and Evening Standard right now.

My normal Readly subscription is less than £8 a month, but they offer a two months for free trial. Even so, at £8 a month, that’s the newsstand cost of just three magazines! If you were after foreign magazines, you’d probably pay more than that for a single issue once shipping was included.

You can get the Readly app with the offer through Amazon (it’s free), and you can read on your phone, tablet, or computer. You can also read offline by downloading the content.


Back To The Future movie posterThis is worth getting. It’s 35 years since Back To The Future was released, and this book – We Don’t Need Roads: The Making of the Back to the Future Trilogy – is the in-depth story of how it was made, with interviews with all the writers, cast, and crew. I was interested immediately, because I always wanted to know the truth about why Eric Stoltz – the original Marty – was recast with Michael J. Fox.

I found out about the book from an MSN newsfeed item, where fans have been arguing about whether any of Stoltz remains in the films (apparently, they reckon it’s Stoltz’s fist when he punches Biff in the café). The book doesn’t answer that, but it’s a damned good read.

It’s 268 pages devoted to one of the best movie trilogies – certainly of the 80s – of all time. And best of all, as well as paperback there’s also a Kindle edition (which is the one I bought). I also note that other books about the movie are available on Kindle Unlimited for free (see the banner on the right for a free trial if you’re interested).


Ennio MorriconeThis one’s likely to pass most people by – I doubt many know who he is. But he represents a huge part of my childhood (and ever since, come to think of it).

Ennio Morricone has died at the age of 91. He was a film composer, but by far his best known works were the themes from The Dollars Trilogy of Spaghetti Westerns in the 1960s. His score for The Good, The Bad And The Ugly in particular is a genuine work of art.

RIP, Ennio.


Eric Idle in Monty Python sketchCouldn’t have put it better myself. Eric Idle has criticised the official Monty Python Twitter feed for tweeting “It’s time to dust off your finest attire now that pubs & restaurants are open from tomorrow.”

Idle’s response was:

Do not listen. This is shit advice. I have nothing to do with this. In the wise words of my wife. “What has changed?” Nothing. There is no cure, there is no vaccine. Go out at your peril. Mingle at your own risk. Just remember “Bring out your dead.”

Unless your pub is called The Grim Reaper, you should stay home. Please be safe.

Completely agree, Eric. It’s too soon.


The Jen Fog fogging machineRegular readers will know I have referred to JennyChem before, mainly in my article about smearing windscreens. I buy their brand of TFR.

I got an email from them today announcing the launch of their new defogging machine, which claims to do anti-viral sanitising as well as removing tobacco and pet odours. It can be used in cars and for treating small living spaces. It’s called The Jen Fog.

At £145, it’s quite a bit cheaper than other fogging machines, and it comes with 5L of the fogging liquid. Each treatment takes about 20 minutes.

The fogging liquid itself costs £17.50 for 5L. You can even choose between unfragranced, Cherry, Tea Tree and Pine, Strawberry, and Bubblegum scents.

The machine has a 400ml reservoir, and each fill will treat up to 30 cars. So a 5L bottle will be good for up to 375 treatments!

Those numpties looking at buying things to clip on to their air vents should invest a little more – actually, only three times more, because they’re being ripped off with those dinky things – and buy the real McCoy. If anything is going to sanitise the car properly, it’ll be something like this – which is much more cost-effective than some of the prices for ‘refills’ I’ve seen being bandied around social media.

If anyone is interested, these are the datasheets for the FogSan fluid, and it has been tested and confirmed as a viricide.


Product Spec Sheet


Three American MoronsAmerica has a problem. Actually, America has many problems. But with COVID-19, some problems stick out more than others.

Mind you, I say that. But in America right now, pretty much all problems stick out. One of the current ones is in Texas. It seems they have had daily new cases of COVID-19 jump from 2,000 to 6,000 (the article says 5,000, but it is actually 6,000 right now) in a few weeks. Putting that in perspective, Texas has a population which is about a third of the entire UK, yet our maximum number of daily cases has never – apart from one day in April, where I think care homes were added – been much above about 6,000. And the charts indicate it is still accelerating in Texas.

Of course, we had the lockdown. And apart from a worrying number of morons ignoring it, that has brought our daily cases down to around 1,000.

In a similar vein, Texas has seen around 150,000 cases overall. So far. That’s already half of what we’ve seen with three times as many people, and a higher population density.

America has a complicated political structure, whereby state government mainly calls the shots, but this is further complicated by the various amendments to The Constitution, meaning the people pretty much decide whether they follow the Law or not (it’s the ‘Land of the Free’, after all). And if anyone tries to make them, they get their guns out and it gets even more complicated (it’s also the ‘Land of the Stupid’ at the best of times). And all this is completely legal, thanks to that same Constitution.

You could write forever about the American system. But the point I wanted to make was about wearing face masks. It seems that the Texas Governor has urged people to wear masks ‘where it is indicated’. This has proved unpopular – violently so, from what I can gather. And my question in the title is simply illustrated by the photo from the BBC.

See if you can spot the morons in it. Hint: there are three of them, and I’ve numbered them just in case you can’t work it out.


Flip-flops - the most inappropriate driving shoesOriginally published in 2019, so references to ‘recent’ apply to 2019.

With the weather we’ve had recently, there’s a good chance you’ll have had pupils turn up half naked for their lessons ready to sweat all over your seats (one of mine has been bringing a towel to sit on after I ribbed him about wetting the seat). Then, five minutes later, they’re moaning about being too cold because you have the aircon turned on (assuming you’re not a tight-arse who refuses to turn it on to save fuel).

One issue which comes up regularly throughout the year, though, is what they have on their feet.

At the most basic level, a new driver has got to learn how to control the pedals, and especially the clutch. To do that, they’ve got to be able to feel it – which they can’t if they’re wearing big, clunky shoes. Running shoes are probably the worst for this, because they’re specifically designed to absorb shock (and therefore any light touch on the pedals), but any kind of shoe with a platform is going to make clutch control harder. This is especially true if the pupil hasn’t driven before, and even more so if they’re one of the types who is going to have problems in this area anyway.

I had a pupil a few years ago who was one of the jumpy kind. One day I picked her up directly from work, which meant she had ‘forgotten’ her driving shoes. She was wearing platformed Doc Martens – literally, with a four inch chunky heel and bulldozer tread underneath. I abandoned the lesson after less than ten minutes before someone was killed, and drove her home. In a similar vein, I remember once seeing a woman get out of a Mini Cooper wearing massive goth boots with wedge soles that were at least three inches thick (below the knee, she was a ringer for Karloff’s Frankenstein). You cannot drive safely in those. Period.

I always advise pupils to wear flat soled shoes with a thin profile. Anything thick is going to make life difficult, and it drives me crazy when one turns up for their very first lesson in designer running shoes, with the extra thick sole and a concealed wedge heel.

Speaking personally, I absolutely hate it when they want to drive barefoot. My reasoning behind this is that I know from direct experience that you can stub your toe or even cut your foot on the pedals if you hit them in the wrong place at the wrong time, and it bloody hurts. Car manufacturers don’t seem to put much effort into ensuring the undersides of the pedals free from burrs or sharp edges. Furthermore, there is no way most people can brake as hard barefoot as they could in shoes. And if it’s more than half an hour since the car was last valeted, the floor mat will have grit on it, and the last thing you want is to have to execute an emergency stop in your bare feet only to discover something sharp stuck on your sole.

Having said that, I had one pass recently who drove barefoot. I let her do it (after telling her off the first time for trying to stow her shoes in the footwell) after I’d done my usual test in this situation: the Emergency Stop. If they can execute an Emergency Stop barefoot to the standard I expect, then they can drive like that if they want (though I still don’t like it). And she could. However, at the same time she had referred a friend to me who was in the same Halls of Residence, and she couldn’t. One day a few months ago, she came out to a lesson wearing huge furry slip-on slippers (‘why’ was a long story which I’m not sure I fully understand even now). She immediately knew they were not good for driving and asked if she could drive barefoot.

I said that I didn’t mind (because her friend did it), but I was concerned about how well she would be able to operate the brake in bare feet. I asked her to brake firmly while we were stationary and to tell me how it felt. She said it hurt, and she didn’t think she’d be able to brake hard if she needed to on the lesson. Problem solved, and we rescheduled – with the additional light-hearted warning not to come out with the wrong shoes again.

I can think of loads of examples where pupils had previously worn sensible shoes, then come to lessons wearing different though not necessarily inappropriate ones, and had a stinker – just because the shoes are different! Small differences can have a huge effect on some people.

Pupils with larger feet also need to be careful. Anything much above size 9 or 10 doesn’t work well if their shoes have long toe caps, because they’re likely to start catching on the cowling above the pedals. Winkle pickers are a no-no if you have large feet in many normal cars, and since they often have absolutely no grip (just a thin, shiny sole), the risk of the wearer’s foot slipping is also greater.

Very wide- and loose-fitting shoes – Ugg boots spring to mind – are also potentially dangerous, because if you try to slam on the brakes there’s a good chance you’ll make contact with the brake and gas pedals at the same time. And it does happen – it happens sometimes even with small-footed people wearing sensible shoes, so throwing Uggs into the mix is just asking for trouble. The same is true when someone insists on wearing some sort of hobnailed boot two sizes too big as a fashion statement – they’re too bloody wide.

Probably the most dangerous shoes for driving, though, are backless types. Mules, backless sandals, and flip-flops. It’s not necessarily anything to do with the heel thickness – though it can be if they’re platformed – but the fact that they can slip off. I mean, think about it. You can potter about as much as you like in summer wearing flip-flops or mules, but try to run and it’s 50-50 whether they will stay on, and 50-50 whether you end up flat on your face on the pavement or road. They present the same risks in the car if you have to move your foot suddenly to brake – with the additional chance that they will fall under the pedal and prevent you from depressing it fully. They could even get tangled up sufficiently to prevent you being able to brake at all. And don’t dismiss that out of hand – I once had a loop in a shoe lace double bow get itself completely over the clutch pedal (God knows how) so I couldn’t take my foot away or lift it high enough to declutch, and when I slipped the shoe off it swung under the pedal and stopped me declutching fully anyway. Shit happens, as the saying goes.

Strap-on sandals are not so bad, though the open toe arrangement still means you can catch your foot more easily if the sandals are particularly large and oversized (which many are these days).

And it goes without saying that trying to drive in high heels is just plain stupid. The heel messes up how you have to operate the pedals, and you cannot get anything like the same force if you really needed it. Many high heels have shiny soles with little grip, which makes matters even worse.

It isn’t illegal to drive barefoot, nor are any specific types of footwear banned or even mentioned in the Highway Code. The only reference is in Rule 97 (partial quote):

Before setting off. You should ensure that

  • clothing and footwear do not prevent you using the controls in the correct manner

However, DVSA has been quoted separately as follows:

Wear sensible clothing for driving, especially on a long journey. Suitable shoes are particularly important. We also would not recommend driving barefoot because you don’t have the same braking force with bare feet as you do with shoes.

My comments above are based purely on my own experience and knowledge, and they agree completely with this DVSA advice. And so do various other organisations.

I wear flip-flops and never had a problem

This stupid argument makes me angry – especially when it is coming from ADIs.

Everyone knows that if you have a set of expensive crystal glass goblets you shouldn’t drop them. If you do, they’re likely to smash. However, someone somewhere will undoubtedly have dropped one by accident one time, and it will have bounced on the carpet or the arm of a chair, and survived. This does not mean it is OK to drop or mishandle delicate glass goblets. It just means you were bloody lucky.

As I said above, if you try and run in flip-flops or mules, they’re easily likely to come off or send you sprawling (possibly both). The chances of that happening are roughly the same as they are of you getting away with it. If personal injury is one of the possible outcomes, then those odds are not good. If death for you or a passer-by were a possible outcome, they’re catastrophically bad.

There’s no evidence flip-flops are dangerous

You really shouldn’t just say what comes into your head before you’ve fact-checked it. Back in 2016 the insurance company, Sheila’s Wheels, did a survey – and it was of enough people to have statistical significance across the population –  which showed inappropriate footwear was responsible for as many as 1.4 million accidents a year in the UK. Of those surveyed, 60% admitted to driving in ‘inappropriate footwear’. A third said that this involved sandals and flip-flops. And a quarter said they still did it in spite of their previous mishap. About one twentieth to one tenth had actually had an accident as a result.

It doesn’t matter that more people have accidents opening a tin of beans, or taking a sheet of paper out of their printer. Those things have nothing whatsoever to do with driving a car. What matters is that flip-flops are demonstrably dangerous when worn for driving.

I drive in high heels and don’t have a problem

There is no way you can drive as safely in high heels as you can with sensible flat soles. Period. It is a simple scientific fact based on the change to the way you have to apply leverage to the pedals when a high heel is extending and deforming your foot length. Having to brake hard in an emergency situation is going to be a lottery if there is the chance of your four inch heel making contact with the floor before you’ve got the brake on hard enough, or if it snags on the mat.

Remember the example I gave above, of the woman in the goth boots? Three inches of plastic increasing her leg length by 10% and suppressing all feeling of the pedals? Driving in high heels is no different – possibly worse – and anyone who suggests otherwise is a complete idiot, even if they have “always done it”. That’s the risk you’re taking each time you drive in heels.

Pupils will drive in those shoes when they pass

That’s their problem. Your job is to try and educate them in what’s right and what’s stupid while they are with you – not to encourage them in dangerous practices.

I advise all of mine to keep a pair of driving shoes in the car when they pass and not to risk it with heels. Beyond that, it’s up to them.

It’s not against the Law to wear flip-flops

Well, you’d probably still be arguing the toss even if it was. But the fact that it isn’t specifically against the Law doesn’t mean it is the sensible or right thing to do. That it isn’t specifically against the Law means that you doing it is your problem as you struggle with simple common sense. But if you’re encouraging others to do it, then you have become the problem.

But you let people drive barefoot

And I don’t like it. I only give in if they can prove to me that they can do an Emergency Stop properly. As it is, I can count on the fingers of one hand the number who have done it out of many hundreds I have taught. Quite frankly, I wish they would make it illegal to drive barefoot or in inappropriate shoes.

What shoes do your wear?

Deck shoes. I suggest to my male pupils they drive in something similar if they have any issues on lessons. I suggest to the females that ballet pumps with a firm sole are worth a try. It’s surprising how many times I explain – diplomatically – that a driving lesson isn’t a fashion shoot, and people should be comfortable ahead of looking like they’re going to an opera.

Why shouldn’t you put your shoes or bag in the footwell?

If you brake, whatever is down there will move forward. The only place for it to go is under the pedals. So if a kid on a bike rides out in front of you and your bag has moved under the brake or clutch, one of you will be in hospital (or worse) and the other will be up on a careless driving charge (or worse) and about 99% of the way towards becoming an ex-ADI.

Putting your shoes or bag in the footwell isn’t a problem

I have a tidy bag on the back seat of my car for a good reason. On more than one occasion during my driving lifetime, sharp braking has resulted in a bottle or book sliding under the seat and straight under the pedals. The design of the car footwell and the universal laws of physics guarantee that loose objects will end up there if you brake hard. Shit happens.

Storing anything in the footwell is dangerous. I regularly get people wanting to put their shoes, handbags, and even an umbrella (surprisingly common) down there. I simply won’t let them. Because I know from experience how dangerous it is.


COVID SOM imageJust saw this in the news. Driving lessons can recommence from 4 July 2020.

I’m now going to have to let most of my pupils go, since I cannot start immediately as I am still isolating to protect my elderly parents. And it’s too soon, anyway (we can’t socially distance, and far too many new cases of the virus are still occurring daily).

On the plus side, there will be no more idiotic social media posts about ‘when can we go back’ and ‘well, technically, we never had to stop’.

And the official DVSA email has now come through.


The Chillmax AirI wrote this in the summer of 2019, but started to see blanket adverts for the device – or identical devices – in 2020. The prices are ridiculous in some cases.

Be aware that the device does not work to anything like the levels these ads claim. So be careful. The original article follows.

Early in July 2019, I saw the Chillmax Air advertised on TV in one of those shouty ads. Then, the same evening, I was shopping in Asda and saw it on display. I am an idiot for things like this, and bought it on impulse so I could test whether it worked or not.

As a chemist, I’m well aware that in order to cool a large space effectively you’re going to need something with a big fan and a special refrigerant. In practical terms, that means a fairly large device holding a motor-driven compressor, a closed radiator filled with the refrigerant, a fan to suck air in and blow it across the radiator, and a wide exhaust pipe through the wall or window to get rid of the “removed heat”. In many cases, you also need to collect or drain the condensed water that comes out of the air as it cools. A typical air conditioner for a small or medium-sized room will be about the size of bedside cabinet. The Chillmax Air is not much bigger than six CD cases glued into a cube.

If you’ve used a normal desk fan you will know that you only feel “cooler” if you’re sweating a bit. That’s because the fan evaporates your sweat as it pushes air over it, and that evaporation is accompanied by a small cooling effect – it’s called “evaporative cooling”. If you’re not sweating, you don’t feel any cooler. Conversely, if the surrounding air is very humid, then no matter how powerful your fan is, you will feel little or no cooling because sweat can only evaporate if the air has capacity to hold additional moisture (I’ll explain that a bit more later, because it is really the factor that determines whether the Chillmax is any good).

As an aside, many liquids exhibit the evaporative cooling effect. In the case of diethyl ether (the stuff they used to use as an anaesthetic), if you force it to evaporate very quickly you can even freeze water (if you do it properly). However, ether is both highly flammable and toxic, so apart from demonstrating it in the school lab (where I remember it from, along with the massive headache it gave me), it doesn’t have much practical application these days. Early refrigerators used it, which was spectacularly dangerous.

The Chillmax Air uses the evaporative cooling effect of water, and this is much less than with ether – similar to sweat, in fact. The unit consists of a reservoir at the top, which you fill with normal tap water, and this drips down on to a radiator unit which has ten sideways-stacked fibre panels in it through which a fan blows air. The water evaporates from the fibre panels, and the evaporatively cooled air comes out through the front grille. According to the marketing spiel on the TV ads, you’d be forgiven for thinking you’re going to get frostbite if you sit too close. I knew this wasn’t going to happen, but I wanted to know just how effective the Chillmax was.

When I first set it up and turned it on, the first thing I noticed was that the fan is quite powerful, so you get a good flow of air directed at you – but note that that it’s only about 5″ in diameter, so it can’t beat a proper desk fan for air flow. The air did seem a little cooler compared with what my desk fan was blowing at me, but it also felt ‘softer’ – that’s very important, and I’ll explain later. But the big question was how much cooler was the exhaust air?

I fired up my trusty data logger and left it in front of my desk fan for 30 minutes for the control data. Then I moved it and suspended it in front of the Chillmax for the same period of time. This is what it recorded (red line is the switch over point).

Chillmax - temperature log in hot and sticky conditionsThe ambient temperature where I ran the test was about 29ºC. The Chillmax brought this down by about 4ºC.

So, the Chillmax definitely cools the air that passes through it. Let’s work on the assumption that it would be able to get the same 4ºC drop no matter what the ambient temperature was. If your room is 38ºC, pulling it down to 34ºC still means it’s bloody hot. And also note that since the Chillmax is physically so small, the cooling is very localised – it won’t cool a room down.

But there’s more to it than that. I mentioned that the exhaust from the Chillmax felt ‘softer’. I knew what it was, but my data logger shows it in numbers.

These are is the data for relative humidity recorded at the same time as the temperature measurement, above (red line is the switch over). The humidity went up dramatically.

Chillmax - RH log in hot and sticky conditionsAs I’ve already explained, the Chillmax works by evaporating water on fibrous panels by forcing air across them. That water has got to go somewhere, and in this case it comes out as vapour in the cooled air. In the right light, you can actually see it – it’s essentially fog. And just like when it’s foggy outside, and everywhere gets damp, this vapour can condense on surfaces. My data logger collected some and began to drip during the test, and I have since discovered that it also condenses on the front grille and can drip periodically, so you’d need to be careful what you had underneath it if you placed it on a shelf. The fan is quite powerful enough to project the drips forward slightly when they drop.

The ambient humidity in the room where I did the test was about 44%RH. The Chillmax sent that up to over 70%RH.

It’s this elevation of the humidity of the cooled air which really brings into question whether the Chillmax is worth the investment. You’re probably aware that you can have a hot summer day in the high 20s where it is pleasant and comfortable, but a cooler and overcast day might be horribly sticky – or muggy. That’s because of the humidity, or water vapour in the air.

The amount of water vapour that air can hold varies with the temperature. Once you reach the maximum, any extra vapour condenses out – misted up windows, dampness, even drips and pools of moisture on window sills or under lamp posts. Cold air can only hold a small amount of moisture before condensation occurs, but hot air can carry much more. Although ‘humidity’ technically refers to the amount of water in the air, the figure most people are referring to when they say it is relative humidity. This is the amount of moisture in the air expressed as a percentage of the maximum amount it could hold at that temperature, hence the units %RH. It’s a very complicated subject, but the important factor for us here is that when it is warm or hot, higher relative humidity is uncomfortable. Indeed, you may have seen weather forecasts where they give the actual temperature and the ‘feels like’ equivalent – that’s a reference to the ‘heat index’, which takes into account the effect of the %RH. Here’s a graphical chart for that.

Heat Index - graphical representationAs an example, if the temperature is 30ºC and 50%RH, it will feel like 31ºC. If the humidity goes up to 80%RH, then it will feel like 38ºC. If the temperature is 35ºC at 50%RH, it will feel like 41ºC. But if the humidity goes up to 80%RH, it’ll feel like 57ºC! The calculation for this is complex (you should see how long my Excel formula for it is) and non-linear, and the increase in ‘feels like’ is greater at higher temperatures. It also contains an element of opinion/perception, which is why there’s no point using numbers above about 60ºC, but it is what the forecasters use. Incidentally, the official health designations for the colours are: yellow – caution; amber – extreme caution; orange – danger; and red – extreme danger.

This is where the problems come in for the Chillmax Air. If it’s 35ºC and 40%RH, it’ll feel like 37ºC. Cool the air to 31ºC and send the humidity up to 80%RH, and it’ll feel like 41ºC. So it’s actually hotter in terms of comfort. Do the same comparison when the surrounding temperature is 38ºC, and the ‘feels like’ goes from 43ºC to over 50ºC!

At lower temperatures the Chillmax will produce a slight net cooling effect, but at higher temperatures – the ones you likely to be wanting to use it in – it makes things worse. But even at these slightly lower temperatures, the full 4ºC drop is cut somewhat simply because higher humidity makes it feel warmer.

Proper air conditioners remove water from the air they cool – so much so that the best ones have humidifiers in them to stop the cooled air from being too dry. This removal of moisture is why the air from proper air conditioners feels crisp, as opposed to the ‘softness’ of moist air. The Chillmax does the opposite of normal A/Cs, and adds moisture.

Aesthetically speaking, the Chillmax is a cube – more or less – about 15cm along each side. There are two buttons on the top rear, one which changes the fan speed to one of three settings (or off), with a blue LED for each, and another button that turns the night light on or off. There’s a flap on the top front through which you add the water. The radiator system is a plastic-framed insert which you access by pulling the front grille out. It slots in and out easily. You can’t officially replace the fibre inserts in the radiator, but you can buy the whole radiator assembly from JML for £15. My only major gripe is the power cable. The jack plug that goes into the Chillmax is quite stubby and doesn’t go into the socket very far, so it is easy to dislodge it. However, the cable itself is quite long, and the  mains plug is a moulded UK type.

JML claims the Chillmax can run for up to 10 hours per fill, but this is undoubtedly on the lowest of the three fan speeds. At top speed, it runs out in less than three hours. To be fair to it, you do still get a cooling effect on the lowest speed, and since the water lasts longer then, less of it will be getting pumped into the air at any one time.  JML sells the humidification as a positive without relating it to the comfort relationship between temperature and %RH, but note what I said above. If you want to cool down in humid weather, it isn’t just the temperature that needs to come down, certainly not a mere 4ºC drop, and definitely not if that means pushing high humidity even higher.

Does it really work?

Well, it does cool the air by a few degrees, but it also sends the humidity up. So if it is already humid and sticky, the cooling effect is completely cancelled out by the extra stickiness. If it’s really hot, then no, it doesn’t work.

Will it cool more if I use ice water?

No. Evaporative coolers are not influenced significantly by the temperature of the water used in them. The temperature of the air that comes out depends on the temperature (and humidity) of the air going in, and the science of evaporation.

Can I use it to cool my PC?

Someone found this article on the search term “jml chillmax air for pc cooling”. If they mean what I think they mean, no, there is absolutely no way you want to be blowing damp air into your PC.

Can you get larger versions?

You can certainly get larger evaporative coolers. The working principle is that the larger the surface area of water, and the greater the airflow over that water, then the greater will be the possible drop in temperature at the front end. However, cooling effectiveness is influenced greatly by the RH of the air going in.

If the air is very dry, then a large evaporative cooler might be able to drop inlet air at 30ºC down by as much as 10ºC. However, if the inlet air is very humid, the temperature drop could be as little as 1ºC. In the UK, the realistic temperature drop you could expect on a non-humid day for a large cooler would be around 5-6ºC, but on a sticky day you’d only get about a 3ºC drop.

Suppliers of these devices say that they need good ventilation or extraction, and I would imagine that’s so the humid air can escape. If you’re evaporating more water to get better cooling on larger devices, you’re also producing a lot more water vapour. Be careful if you read any of the reviews – people may have noticed cooling in already cooler conditions, but trust me – if it’s very warm and humid, you will not notice any effect.

So, does the Chillmax work?

It cools the air by a few degrees. In that sense, it works. But it sends the humidity of that air up considerably, and this cancels out the benefits of the cooling effect in the instances where I tried it. The ‘heat index’ is the key issue, as explained above.

Only the air being directed at you is cooler. The device cannot cool down a room. It’s far too small for that.

The increased humidity does produce condensation, so you have to be careful to keep it away from electrical sockets where it might drip on them. The cooler also contains a fair volume of water when full, so you don’t want to knock it over.