What's the blue square in the hotel?

The blue square in a hotel is generally solid, and its internal structure may be composed of many materials. Perhaps the most commonly used sponge is used to absorb and decompose the odor and impurities in the liquid. In addition, the blue square may also contain activated carbon particles, which are used to adsorb particulate matter and harmful gases in the air.

However, the exact definition and use of blue squares in hotels may vary from hotel to hotel and region. Some hotels may use squares of other colors, or even use different shapes and materials to achieve the same effect.

Therefore, if you need accurate information about the blue square of the hotel, you'd better consult the hotel staff directly.