After interior decoration, the emission time of formaldehyde varies depending on many factors, including the materials used, ventilation conditions, indoor temperature and humidity, etc. Generally speaking, formaldehyde concentrations will gradually decrease over time, but it may take months or even years to completely dissipate.

Typically, the following points can help reduce formaldehyde concentrations:

1. Ventilation: Maintaining good ventilation can accelerate the emission of formaldehyde. You can open windows and use fans to promote air circulation.

2. Use adsorbent materials such as activated carbon: Adsorbents such as activated carbon and bamboo charcoal can help absorb harmful indoor gases.

3. Plants: Some indoor plants such as spider plants, aloe vera, etc. are believed to improve air quality and help absorb formaldehyde.

4. Choose low-formaldehyde materials: When decorating, try to choose environmentally friendly, low-formaldehyde materials.

5. Regular testing: Formaldehyde detection equipment can be used to monitor indoor air quality to ensure that the formaldehyde concentration is within a safe range.

It is generally recommended that after renovation, try to wait a few months under well-ventilated conditions before moving in, and regularly check indoor air quality to ensure safety.