Ventilation Day (Kanki no Hi)
Wordplay AnniversariesNovember 9th Is "Ventilation Day"! The Origin and Importance for Protecting Your Health
November 9th is "Ventilation Day" (Kanki no Hi), a day for refreshing the air indoors and creating a healthy living environment. This anniversary was established in 1987 by the Japan Electrical Manufacturers' Association (JEMA). The origin comes from a play on numbers — "11" is read as "ii" (good) and "9" as "kūki" (air), together forming "ii kūki" (11/9 = good air).
November is when autumn deepens and people start using heating equipment. Using heaters tends to make indoor air dirtier, and dryness can make viruses more active — so this is a time when raising awareness about ventilation matters most.
We take in about 15 kg of "air" into our bodies every day. Adjusting the quality of the air we consume — even more than what we eat or drink — is one of the most basic and important habits for maintaining health.
Why Is "Winter Ventilation" Especially Important?
In winter, we tend to keep windows closed to avoid letting the room temperature drop. But this causes carbon dioxide levels to rise, which can lead to drowsiness and headaches. Creating proper airflow is also essential for preventing mold caused by condensation.
[Thorough Comparison] 24-Hour Ventilation System vs. Opening Windows — Which Is More Efficient?
Many people wonder, "If I have a 24-hour ventilation system, do I still need to open windows?" In fact, the two serve different roles.
- 24-Hour Ventilation System: Designed to replace all the air in the house once every two hours. Excellent for maintaining ongoing air freshness.
- Opening Windows: The appeal is its immediacy — exchanging a large volume of air in a short time. Ideal after cooking or when guests visit.
Rather than relying on just one method, the optimal solution for 2026 is "hybrid ventilation" — relying mainly on your system while periodically opening windows as well.
Comparing the Pros and Cons of Ventilation Methods
| Comparison | 24-Hour Ventilation System | Opening Windows |
|---|---|---|
| Efficiency | Low to medium (sustained) | Very high (immediate) |
| Effect on Room Temperature | Minimal (heat-exchange types can maintain temperature) | Significant (rooms get cold quickly in winter) |
| Pollen / Dust | Can be removed by filters | Enters directly |
| Convenience | Just flip a switch | Requires opening and closing windows |
| Recommended Scenarios | Always (including while sleeping or away from home) | While cleaning, upon waking, upon returning home |
The Latest for 2026! "Pro Ventilation Techniques" That Keep You Warm While Cleaning the Air
- Practice "Two-Stage Ventilation": Slightly open a window in an unoccupied room and let the air travel through the hallway to the living room. This ventilates the space without lowering the perceived temperature.
- Use a Circulator Together: Point it toward the outside window to forcibly expel dirty air. Ventilation can be completed in about 5 minutes.
- Introduce an IoT Air Quality Sensor: Visualize CO2 levels and ventilate only when necessary, preventing unnecessary cold air from entering.
Don't Forget! Maintaining Your Ventilation Fans
If the filter on a ventilation fan is clogged, its ventilation capacity drops to less than half. Use "Ventilation Day" as an opportunity to clean your kitchen range hood and bathroom exhaust fan, and restore their original performance.
Summary: On November 9th, Replace the "Good Air" Throughout Your Home
November 9th, "Ventilation Day," is a day to pay attention to the quality of the air you can't see, and to protect your family's health and the lifespan of your home.
- Origin: The wordplay "11 (ii) + 9 (kūki) = ii kūki" (good air).
- Key Point: "Hybrid ventilation," combining a 24-hour system with periodic window-opening, is ideal.
- 2026 Tip: Use sensors and circulators to ventilate smartly and efficiently in a short time.
Refreshing the air can also refresh your mood. This November 9th, try opening your windows wide and breathing in the crisp autumn air.