1. Ordinary charcoal has a certain adsorption capacity, but its adsorption capacity is unstable and easily affected by environmental changes. It may absorb other substances and even release formaldehyde adsorbed on charcoal again when it reaches saturation.
2. One type of product in charcoal is activated carbon, which has a better formaldehyde removal effect than ordinary charcoal. However, activated carbon has a smaller adsorption capacity, and it usually fills up after being left for a short time. Moreover, if there is too little, it will not be effective.