The invention relates to the technical field of devices for 
formaldehyde removal, and discloses a practical intelligent reminding device for 
formaldehyde removal. The device includes a casing, whereina mixed liquid is arranged inside a closed box, a transparent glass plate is connected to a position right above the closed box, and a 
photoresistor is arranged right above the transparent glass plate; and a 
sodium hydroxide solution is arranged on the left side of the inner part of a filter box, an 
activated carbon adsorption plate is connected to the interior of the filter box, and a quicklimelayer is connected to the interior of the filter box. After 
chlorine gas is introduced into a 
hydrogen peroxide solution, 
peroxide ions are oxidized into 
superoxide ions firstly, a further reaction isperformed on 
formaldehyde and the 
superoxide ions, and a reaction is performed between formaldehyde and 
hydroxide ions further; since the 
superoxide ions are extremely unstable, 
excess energy is released in the form of photons when excited-state 
oxygen atoms are turned into ground-state 
oxygen atoms, and the resistance value of the 
photoresistor can be changed through the brightness of 
red light,so that the content of indoor formaldehyde is predicted further, the transfer amount of 
chlorine gas is controlled accordingly, and waste of materials is avoided.