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<\/p>\nHello, everyone.<\/p>\n
This is Enta.<\/p>\n
As July draws to a close, the job site has gone into full-blown extreme heat mode.<\/p>\n
I received more feedback than I expected on my recent article titled \u201cTake Off Your Work Clothes with a Fan When the Temperature Exceeds 35 Degrees.\u201d<\/p>\n
While some people agreed, there were also quite a few who said, \u201cNah, I\u2019m fine even at 40 degrees,\u201d lol.<\/p>\n
Everyone perceives heat differently, but since numbers serve as a standard, we can\u2019t be vague about them, can we?<\/p>\n
But that's beside the point.<\/p>\n
This is the sequel to that.<\/p>\n
Last time, I talked about external factors like temperature and humidity, but this time I\u2019d like to write about what\u2019s happening inside the body and how the human mind processes it lol.<\/p>\n
Let me say this up front: this article is not meant to disparage workwear with built-in fans.<\/p>\n
I wear it every year, too. It\u2019s just that it\u2019s not \u201cabsolutely\u201d necessary.<\/p>\n
<\/p>\n
What inspired me to write this article was a piece in the September 24, 2024, issue of the Japan Agricultural News titled \u201c[Farmers\u2019 Special Report Team] Work Clothes with Fans: Caution Advised When Using Them in Extreme Heat.\u201d<\/p>\n
It all started with a request sent to the editorial department from a reader in the Tokai region; apparently, a man in his 40s\u2014a friend of that reader\u2014died of heatstroke while working on a farm while still wearing work clothes equipped with a fan.<\/p>\n
As someone who does the same kind of outdoor work, I felt that this wasn't just someone else's problem.<\/p>\n
Actually, I\u2019ve had the experience of wearing work clothes with a fan built in and feeling worse and worse, lol.<\/p>\n
According to the newspaper\u2019s reporting, one major manufacturer responded, \u201cIt is up to the user to decide whether to use the product during a heat wave,\u201d while another manufacturer explained that \u201ceffectiveness decreases in hot environments,\u201d but added, \u201cWe have not set a specific temperature threshold at which use should be avoided.\u201d<\/p>\n
It states that while the effective range of the cooling effect is indicated, the data supporting that claim is not provided, and when asked about it, the response was that \u201cwe are unable to disclose it.\u201d<\/p>\n
This is the part I really wanted to write about this time.<\/p>\n
According to an article published by HuffPost Japan in July 2026, the official X account of Air Conditioning Suit Co., Ltd., the manufacturer of \u201cAir Conditioning Suit\u00ae,\u201d reportedly sparked a buzz by posting a guideline on the effective cooling range.<\/p>\n
It is reported that, in a reply quoting a post by a member of the public stating, \u201cYou should seriously avoid wearing air-conditioned clothing at Comiket,\u201d the company explained that it lists guidelines for the effective cooling range on its website and that \u201cthe cooling effect is virtually nonexistent in orange or red environments.\u201d<\/p>\n
According to the article, the graph identifies the point where the temperature is 35\u00b0C and humidity is 60\u201370% as the \u201ccomfort threshold.\u201d<\/p>\n
The company that makes it actually released the figures on its own initiative.<\/p>\n
Furthermore, the company\u2019s official website clearly states that the temperature range within which the Menstrual Cooler\u00ae is effective is limited.<\/p>\n
The conditions for the cooling performance comparison test are also clearly specified as 30\u00b0C and 50% humidity.<\/p>\n
The line was already drawn from the very beginning.<\/p>\n
Maybe we just didn't notice it lol<\/p>\n
The person mentioned in the article is Ken Tokizawa of the National Institute of Occupational Safety and Health.<\/p>\n
The testing was reportedly conducted in an environment with a temperature of 34 degrees and 50% humidity.<\/p>\n
According to the report, eight adult men walked briskly for about an hour each\u2014once while wearing work clothes equipped with fans and once without them\u2014and changes in their core body temperature were measured via rectal temperature at regular intervals.<\/p>\n
The results showed that core body temperature rose to a similar degree whether the device was worn or not.<\/p>\n
In response to this, Mr. Tokizawa pointed out that, under these conditions, \u201cthe measures were not found to be effective in preventing heatstroke.\u201d<\/p>\n
Isn't that a shock? lol<\/p>\n
A paper in the institute\u2019s Special Research Report, JNIOSH-SRR-No. 53 (2023), also states that the body cooling methods currently in use are,<\/p>\n
It is stated that its primary effects are to lower the skin\u2019s surface temperature and alleviate thermal discomfort, and that its effectiveness in preventing heatstroke is limited.<\/p>\n
\"It's cool\" is a fact.<\/p>\n
However, \u201ccool\u201d and \u201cpreventing heatstroke\u201d are not the same thing.<\/p>\n
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<\/p>\n
Have you ever seen a thermal imaging image in an ad for workwear with built-in fans, where the person is bright red before putting it on and turns blue afterward?<\/p>\n
In an article in the Japan Agricultural News regarding this matter, Mr. Tokizawa explained, \u201cThermography measures skin temperature, which is different from core body temperature.\u201d<\/p>\n
He also stated, \u201cThere\u2019s no doubt that a drop in skin temperature makes you feel cooler.\u201d<\/p>\n
In other words, that image isn't fake. It just shows only the surface of the body.<\/p>\n
That means we're misunderstanding it.<\/p>\n
Heat stroke occurs when the temperature of the body's core\u2014including the brain and internal organs\u2014that is,Onset triggered by a rise in core body temperature<\/span><\/strong>It is a disease that causes...<\/p>\n According to Mr. Fukazawa, whether or not a rise in core body temperature can be suppressed serves as an indicator of whether heatstroke can be prevented.<\/p>\n In the test conducted earlier, it was confirmed that wearing the garment did not affect the rise in core body temperature, but it did lower the skin temperature inside the work clothes.<\/p>\n Even though the skin feels \u201ccool,\u201d heat continues to build up in the core.<\/p>\n I think the scariest part is that the sensations of \u201chot\u201d and \u201cexhausting\u201d\u2014which are the body\u2019s warning signs\u2014are the first to disappear.<\/p>\n There's another alarming figure.<\/p>\n In the previously mentioned JNIOSH-SRR-No. 53 (2023), a study was conducted involving 10 participants in the older adult group (66 \u00b1 4 years) and 10 participants in the younger adult group (28 \u00b1 4 years),<\/p>\n The study compared rectal temperatures after one hour of light work in four different environments with WBGT values ranging from 27.0 to 31.5 degrees.<\/p>\n It has been reported that when the WBGT rises by 1 degree, the corresponding increase in core body temperature is 0.1 degrees in the elderly group and 0.05 degrees in the younger group.<\/p>\n This means that older adults experience a rise in body temperature at twice the rate.<\/p>\n Furthermore, the report states that when working for one hour at a WBGT of 31.5 degrees, the body temperature of the elderly group reached 38.0 degrees\u2014the upper limit specified in ISO 12894\u2014while that of the younger group peaked at 37.6 degrees.<\/p>\n This means that even if the location, time, and task are the same, what\u2019s happening inside the body can be completely different.<\/p>\n Since our workforce is aging as well, I think these figures are something we need to take seriously.<\/p>\n In Experiment 2 of the same report, participants walked for one hour in an environment with a room temperature of 37 degrees and a relative humidity of 50 percent, and the study compared conditions where the fan was turned off versus when it was running, while wearing dry undershirts.<\/p>\n Under the conditions where the fan was turned off, the rectal temperature reached 38.0 degrees, and even when the fan was running, the rise in temperature was only slightly suppressed.<\/p>\n Furthermore, even though they were allowed to drink as much as they wanted during breaks, their sweat loss exceeded their water intake by 0.4 kg and 0.3 kg, respectively, and<\/p>\n It has been reported that this may lead to a risk of dehydration.<\/p>\n Do any of you know anyone who loses weight during the summer? lol<\/p>\n The mechanism that keeps work clothes with built-in fans cool is the heat of evaporation from sweat.<\/p>\n So, to what extent does the concept of heat of vaporization apply?<\/p>\n \"Evaporative cooling keeps you cool!\"\u2014there are plenty of die-hard fans of evaporative cooling on social media, but I think it\u2019s easier to understand if you think of it in terms of a sauna.<\/p>\n It is said that a typical dry sauna has a room temperature of 80 to 100 degrees and a humidity level of about 10 percent.<\/p>\n If you were to pour 100-degree water on yourself, you\u2019d suffer severe burns, but you can stay in a 100-degree sauna for more than 10 minutes.<\/p>\n It is explained that one reason for this is that, because the humidity is extremely low, sweat evaporates rapidly, and the heat of vaporization draws heat away from the body's surface.<\/p>\n In other words, people inside a sauna are running their bodies at maximum capacity to cool themselves through evaporative cooling\u2014which, in principle, is the same thing that work clothes with built-in fans do.<\/p>\n However, when the \u201cl\u00f6yly\u201d\u2014the ritual of pouring water onto the sauna stones\u2014begins, the humidity rises sharply, and it gets even hotter during the \u201caufguss,\u201d when the sauna master fans the steam with a towel.<\/p>\n According to the descriptions provided by each facility, an Aufguss is a treatment that causes humidity to rise sharply, raising the perceived temperature and promoting sweating.<\/p>\n Even though the fan is blowing, it's not getting any cooler\u2014in fact, it's getting hotter.<\/p>\n I hate saunas, and I just couldn't stop getting annoyed when they did the l\u00f6yly!! lol<\/p>\n When humidity rises and the cooling effect of evaporation weakens, if you expose your body to air that\u2019s warmer than your own body temperature, the breeze will blow toward the source of the heat.<\/p>\n The same thing could happen at construction sites in Japan right now during the height of summer. (Actually, it\u2019s already happening\u2014it\u2019s absolute hell lol.)<\/p>\n As noted earlier in JNIOSH-SRR-No. 53 (2023), since workwear with electric fans draws outside air into the garment,<\/p>\n It states that when the outside air temperature is higher than body temperature, a mechanism that raises body temperature is thought to be activated.<\/p>\n According to the report, the body-cooling effect of electric fans can be either effective or ineffective depending not only on room temperature but also on relative humidity and the amount of perspiration,<\/p>\n It is mentioned, citing overseas research, that it may even be harmful in some cases.<\/p>\n The precautions for use on a website specializing in workwear with built-in fans (operated by Fujiwork Co., Ltd.) state that,<\/p>\n It says, \u201cDo not wear this in environments where the temperature exceeds 50\u00b0C, such as saunas, as there is a risk of burns.\u201d<\/p>\n It actually does say there's a limit. It's just at the very bottom of the product page, lol.<\/p>\n The figures in the catalog may be based on global averages of around 30 degrees.<\/p>\n But we\u2019re actually working at sites where it\u2019s 38 degrees and 70% humidity.<\/p>\n I'll be honest here lol<\/p>\n According to an explanatory article by Mr. Tokizawa published in the April 2026 issue (No. 158) of *Safety and Health Consultant*,<\/p>\n Tests were conducted under both high-humidity conditions (room temperature: 32\u00b0C, relative humidity: 80%) and high-temperature conditions (room temperature: 40\u00b0C, relative humidity: 30%), and<\/p>\n Reports indicate that wearing a damp undershirt while using a fan helps suppress the rise in core body temperature and reduces total body sweat output by half.<\/p>\n In other words, its effectiveness has been confirmed up to 40 degrees Celsius and 30% humidity, provided that the inner layer is kept damp.<\/p>\n On the other hand, the manufacturer states that the product should not be worn in environments where the temperature exceeds 50 degrees.<\/p>\n So, what about the time in between?<\/p>\n As far as I could tell from my research, I couldn't find the answer lol<\/p>\n Well, I guess that just means there aren't any results from experiments like that, huh? lol<\/p>\n However, the article also noted that even if temperatures do not reach 50 degrees in Japan\u2019s natural environment, this can still occur at work sites where heat sources are present.<\/p>\n We've been talking about numbers up to this point, but finally, we come to the human aspect.<\/p>\n When I scroll through social media, I see posts saying, \u201cEven when it\u2019s 40 degrees outside, it\u2019s no problem as long as you have work clothes with built-in fans.\u201d<\/p>\n There are also a great many people who say, \u201cI can\u2019t do my job without work clothes with a fan.\u201d<\/p>\n I have no intention of criticizing this. That\u2019s because there are aspects of that sentiment that are well-founded.<\/p>\n The April 2026 issue of *Safety and Health Consultant* mentioned earlier states that there are significant individual differences in the amount of sweat produced, depending on one\u2019s constitution.<\/p>\n It has been reported that when walking for one hour under the blazing midsummer sun, the amount of sweat lost by some people can reach 1,500 mL, while others lose less than 500 mL.<\/p>\n It seems that the more you sweat, the more effective work clothes with built-in fans become.<\/p>\n In other words, if you say, \u201cI\u2019m fine even at 40 degrees,\u201d it\u2019s possible that you\u2019re actually sweating a lot and that the treatment is really working.<\/p>\n However, this also means there is a high risk of dehydration.<\/p>\n The problem is that I end up applying that feeling to the craftsman in his 60s sitting next to me.<\/p>\n As the numbers from earlier show, the processes taking place inside the body are changing at twice the rate.<\/p>\n Just to be clear, there is a valid reason why increasing comfort is important.<\/p>\n The April 2026 issue of *Safety and Health Consultant* states that this may help prevent a decline in concentration and productivity caused by discomfort from the heat.<\/p>\n In an article in the Japan Agricultural News, Mr. Tokizawa stated that even if the method does not prevent heatstroke, it can help reduce the sensation of heat and thirst, and is therefore expected to help maintain work efficiency and prevent a decline in concentration.<\/p>\n In our line of work, maintaining focus is essential to safety.<\/p>\n If you lose your focus while working on a slope, you\u2019ll have an accident before you even get heatstroke.<\/p>\n However, Mr. Tokizawa points out that since the physical strain remains the same, one should not rely on feelings of discomfort or exhaustion,<\/p>\n It is also said that it is important to take breaks and hydrate just as you would when not wearing the device.<\/p>\n From here on, I\u2019m not going to talk about the materials\u2014I\u2019m just going to share my thoughts.<\/p>\n Work clothes with fans aren't cheap.<\/p>\n I got the clothes, the fan, and the batteries\u2014I picked them out myself and paid for them out of my own pocket. 20,000 yen and up... (The batteries are just so expensive, lol)<\/p>\n So when someone tells me, \u201cI hear it doesn\u2019t always work,\u201d I feel like I\u2019m being dismissed.<\/p>\n I mean, at first I was like, \u201cWhat?!\u201d and looked into it while still being a bit skeptical, lol.<\/p>\n It is said that people tend to gather only information that aligns with what they want to believe, while downplaying information that is inconvenient for them.<\/p>\n This is what\u2019s known as \u201cconfirmation bias,\u201d something I\u2019ve written about many times on this blog.<\/p>\n The thought, \u201cI didn\u2019t get sick from this last year or the year before,\u201d certainly feels like strong evidence.<\/p>\n But it\u2019s also a \u201crecord of the days I happened not to fall.\u201d<\/p>\n So the question is, what should we do?<\/p>\n Wearing a damp undershirt and then putting on a fan-equipped work uniform over it\u2014a method Mr. Tokizawa has dubbed the \u201cwater-sprinkling undershirt.\u201d<\/p>\n <\/p>\n This is a follow-up to the previous post by Air-Conditioned Clothing Co., Ltd.<\/p>\n According to an article in the Japanese edition of HuffPost, the company<\/p>\n \"Adding moisture other than sweat\u2014such as by getting your undershirt wet or using water-cooled items\u2014enhances the evaporative cooling effect.\"<\/strong>...he explained.<\/p>\n The original manufacturer recommends wearing a damp undershirt.<\/p>\n All you have to do is soak an undershirt in water, wring it out thoroughly, and put it on.<\/p>\n According to an article in the Japan Agricultural News, cotton is more suitable than synthetic fibers, and since it dries in about two hours in high temperatures, moistening it again with a spray bottle during breaks is said to prolong its effectiveness.<\/p>\n The April 2026 issue of *Safety and Health Consultant* states that the amount of water used to moisten the inner layer is 350 mL, and the heat of vaporization resulting from this amount of water is approximately 200 kcal.<\/p>\n According to the site's explanation, the energy expenditure for standard adult walking (3 km\/h) is approximately 200 kcal per hour, so<\/p>\n Based on these calculations, it appears that the equivalent amount of heat is being dissipated through the primitive method of wetting one\u2019s undergarments.<\/p>\n It costs almost nothing and doesn't require a battery. All you need is a plastic bottle of water and a cotton shirt.<\/p>\n These days, there are even items where you can fill the inner layer with water or put an ice pack in the inner pocket, right?<\/p>\n It really feels like we\u2019ve entered an era of extreme heat where using such products alongside other items has become essential.<\/p>\n Ultimately, work clothes with built-in fans aren't \"bad\" or \"a one-size-fits-all solution,\" are they?<\/p>\n Within the effective range specified by the manufacturer, this is a tool that will genuinely make your work easier if worn by someone who works up a good sweat.<\/p>\n However, once that limit is exceeded, the tool may quietly change its nature, and the most troubling thing is that the person wearing it may not even notice.<\/p>\n Even though my skin feels cool, I'm hot on the inside.<\/p>\n What I'm trying to say is that I'm not telling you to take off your work clothes with the fan attached.<\/p>\n All I want is for you to be the kind of person who can, even just once, ask yourself, \u201cMaybe it\u2019s not working today.\u201d<\/p>\n That single instance of doubt might cause them to take another 10-minute break.<\/p>\n Those 10 minutes might save someone's life.<\/p>\n As you know, the \"what if?\" mindset is particularly effective when it comes to safety measures.<\/p>\n Our craftsmen, myself, and all of you\u2014we all want to be working on-site as usual next summer, too.<\/p>\n Let's proceed with the installation while carefully monitoring the temperature!<\/p>\n <\/p>\n See you later.<\/p>\n <\/p>\n *\"Air-Conditioned Clothing\u00ae\" is a registered trademark of Air-Conditioned Clothing Co., Ltd.<\/p>","protected":false},"excerpt":{"rendered":" Hello, everyone. This is Enta. We\u2019re now in the final stretch of July, and things on site have gone into full-blown extreme heat mode. My recent article, \u201cTake Off Your Fan-Equipped Work Clothes When It Gets Hotter Than 35 Degrees,\u201d generated more reactions than I expected. While some agreed with me, others said, \u201cNo, I\u2019m fine even at 40 degrees\u201d\u2026<\/p>","protected":false},"author":2,"featured_media":66396,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_bbp_topic_count":0,"_bbp_reply_count":0,"_bbp_total_topic_count":0,"_bbp_total_reply_count":0,"_bbp_voice_count":0,"_bbp_anonymous_reply_count":0,"_bbp_topic_count_hidden":0,"_bbp_reply_count_hidden":0,"_bbp_forum_subforum_count":0,"footnotes":"","jetpack_post_was_ever_published":false},"categories":[111],"tags":[314,14458,14459,14460],"class_list":["post-66378","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-safety","tag-314","tag-14458","tag-ef","tag-14460"],"acf":[],"yoast_head":"\nThe fact that age makes a difference<\/h3>\n
I'm sweating, but I'm not drinking enough water.<\/h3>\n
![\"The](\"https:\/\/norimen.net\/wordpress\/wp-content\/uploads\/2026\/07\/5e77d71ad6fcd2703c683e834fb0cd7f.jpg\")
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\nThinking About the Limits of Latent Heat in a Sauna<\/h2>\n
Why You Don't Get Burned in a 90-Degree Sauna<\/h3>\n
What L\u00f6yly and Aufguss Teach Us<\/h3>\n
![\"Effective](\"https:\/\/norimen.net\/wordpress\/wp-content\/uploads\/2023\/07\/1664d56a885cc5061bb5db25c9d4422c.jpg\")
<\/p>\nThe manufacturer states, \"Do not wear at temperatures exceeding 50 degrees.\"<\/h3>\n
Actually, I don't know what it's like between 40 and 50 degrees.<\/h3>\n
![\"The](\"https:\/\/norimen.net\/wordpress\/wp-content\/uploads\/2026\/07\/cdd4bdf917162898d877076ae964c420.jpg\")
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\nWhy Do We End Up Thinking, \u201cI\u2019ll Be Fine\u201d?<\/h2>\n
There are certainly individual differences.<\/h3>\n
The sensation of \"coolness\" is also real.<\/h3>\n
The more expensive the purchase, the more it upsets me when it gets criticized.<\/h3>\n
\"Water-Sprinkling\" Innerwear: So It Doesn't End with Just a \"No\"<\/h3>\n
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