Japan’s innovative ‘human refrigerator’ is helping protect workers and residents from record-breaking heatwaves. It is designed to rapidly cool the body and prevent heatstroke. Industry analysts predict that single-person cooling pods could soon become standard urban street fixtures
As temperatures across the Japanese archipelago soar past hazardous thresholds, a novel technological innovation has taken centre stage in the country’s battle against extreme summer heat.
Dubbed by the public as the “human refrigerator,” the Do Hiemon Box — a mobile, single-person cooling booth — has transitioned from an unusual technological curiosity into an indispensable tool for heatstroke prevention.
Originally introduced to the commercial market in April earlier this year by refrigeration and vending machine manufacturer SDRS Co, Ltd. and distributed by industrial equipment giant TRUSCO Nakayama Corporation, the stainless-steel booth is engineered to rapidly lower human body temperature during dangerous heatwaves.
Japan’s summer of ‘cruel heat’ (Kokushobi)
The deployment of personal cooling booths comes during one of the most oppressive summers in recorded Japanese history.
The Japan Meteorological Agency (JMA) has increasingly relied on the term Kokushobi — translating directly to “cruelly hot day” — to describe periods when ambient temperatures hit or exceed 40°C (104°F).
In late July, Japan logged an unprecedented five consecutive days of Kokushobi conditions. In Tokyo alone, emergency services transported over 450 individuals to hospital care in a single 24-hour window due to acute heat illness, breaking a decade-long hospitalization record.
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For decades, Japanese outdoor labourers and factory workers relied on traditional countermeasures, such as wearable fan jackets (fan-jakketo) and structured hydration breaks.
However, when ambient humidity couples with air temperatures exceeding 38°C (100.4°F), fan jackets simply circulate hot air across the skin, diminishing sweat evaporation and failing to prevent core body temperature elevation.
This physical limit triggered the demand for enclosed, flash-cooling infrastructure capable of providing immediate thermal relief.
How the human refrigerator works
The Do Hiemon Box draws its design inspiration and foundational cooling technology directly from Japan’s ubiquitous frozen food vending machines.
SDRS, known for manufacturing automated frozen-meal dispensers, adapted its high-efficiency insulation and chilling mechanics into a human-sized chamber.
SpecificationTechnical detailOfficial nameDo Hiemon Box (Do 冷えもん Box)Developer/DistributorSDRS Co Ltd / TRUSCO Nakayama CorpExterior footprintSimilar to a standard commercial vending machine (~1.0 m²)Interior height/Cap1.75 metres (5.7 ft) / 150 kg maximum capacityInternal ambient tempControlled at approximately 15°C (59°F)Direct airflow tempApproximately 5°C (41°F) from top and rear ventsPower consumption~0.51 kWh (plugs into standard 100V household outlet)Operational costApprox. 16 JPY (~$0.10 USD) per hour of continuous useSafety featuresAutomatic 20-minute shut-off timer, 3 cooling speed modesPurchase/Rent¥1,500,000 (~$9,200 USD) buy/¥300,000 (~$1,800 USD) monthly rental
Rather than cooling an entire room, the booth isolates a single individual inside a 15°C ambient microclimate.
Once the occupant sits on the internal stool, high-velocity vents discharge 5°C chilled air toward the head, neck, shoulders, and upper back.
These body regions contain large blood vessels near the skin surface, enabling rapid heat extraction from the bloodstream to lower core internal temperature.
To guard against thermal shock or accidental hypothermia, the unit features built-in safety parameters. The active cold-air jets automatically shut off after 20 minutes, preventing users from remaining in direct sub-10°C air streams for excessive periods.
Why flash cooling works
The human body regulates heat primarily through cutaneous vasodilation and sweating. Under extreme heat stress (above 40°C), cardiovascular strain increases as the heart pumps significantly more blood to the skin to dissipate thermal energy.
When an overheated individual enters the Do Hiemon Box, two physiological cooling stages occur:
Immediate surface relief (minutes 1-3): Chilled air contacting the carotid arteries in the neck and vertebral vessels rapidly cools arterial blood flowing toward the brain, reducing symptoms of heat exhaustion such as dizziness, headache, and acute lethargy.
Core thermal stabilisation (minutes 5-10): Clinical evaluations released by SDRS indicate that a 5-minute session provides noticeable subjective relief, while a 10-minute stint reduces elevated body temperature back toward physiological baseline without triggering intense shivering or cold-induced peripheral vasoconstriction.
Where the ‘human refrigerator’ is being sold
TRUSCO Nakayama targets the product at commercial enterprises, industrial site operators, and public sector organizations rather than individual residential consumers.
Mobile job sites where building permanent air-conditioned break rooms is impossible or cost-prohibitive.
High-heat indoor environments where ambient warehouse temperature management is inefficient.
Public administrative centres, such as Maebashi City Hall in Gunma Prefecture, which installed units in public lobbies as emergency cooling stops for vulnerable residents during heat alerts.
Concert venues, sports facilities, and shipping yards where outdoor workers face extended sun exposure.
The booth’s power efficiency is one of its primary commercial advantages. Consuming roughly 0.51 kWh on a standard 100V outlet, it operates on about half the energy required by conventional spot air conditioners, with run costs hovering near 16 yen per hour.
Outfitted with heavy-duty caster wheels, two workers can relocate the booth across a job site as project needs shift.
However, the public response remains divided between appreciation for functional engineering and concern over climate adaptation trends:
Workplace safety experts and industrial managers praise the booth as a practical device that saves lives on construction sites where traditional air conditioning is unfeasible.
Meanwhile, environmental commentators have voiced concerns, arguing that relying on individual cold pods represents a technological band-aid for global warming rather than a systemic solution.
Health professionals also point out that users exiting a 15°C booth back into 40°C heat must allow brief acclimation periods in shaded transitional areas to prevent acute vascular headaches or dizziness caused by rapid temperature shifts.
Industry analysts predict that single-person cooling pods could soon become standard urban street fixtures in major metropolitan transit hubs, outdoor sports venues, and tourist districts throughout Japan and other high-heat climate regions.
With inputs from agencies