Temperature: warm for the day, cool for sleep

One room, two right answers: 21–22 degrees by day, 18–20 at night. The device shows the air temperature, not that of its own circuit board.

Which numbers are normal

The zones on the device screen. Colour appears only where attention is needed.

GOST 30494-2011 table 1; SanPiN 1.2.3685-21 table 5.27; WHO 2018 — not below 18 °C

Real frames from the device, captured on 4 September 2026.

WHO calls 18 °C the safe winter minimum for a home: below it blood pressure and blood viscosity rise, and respiratory illness flares more often.
For sleep 18–20 °C is best. Above 24–25 sleep fragments: less deep and REM sleep, more awakenings. Humid heat is worse than dry, and the body does not adapt to it in five nights.
Work performance peaks around 21–22 °C. At 30 °C it is about nine percent lower.
The device subtracts its own heat: inside the body it is warmer than the air, and without correction the reading would be a degree or two high.

WHO Housing and Health Guidelines 2018; Okamoto-Mizuno & Mizuno 2012; Seppänen, Fisk, Lei LBNL 2006

Hints in words on the screen. Actions about the room, not about the body.

“Close the windows and curtains” — on a hot day, when outside is warmer than the room.
“Now open up” — in the evening, when outside has cooled below the room.
“Too warm for sleep” — if it is above 24 °C by evening.

Why does the wall thermometer say something else?
Air by the wall, by the window and in the middle of the room differs by a degree or two. The device measures where it stands: on the desk, at breathing height.