Formalin is not considered the right choice for mixing directly with the mushroom raw material or substrate. Authentic cultivation and agricultural sources state that formalin or formaldehyde is mainly used in limited amounts for sanitising mushroom farm rooms, equipment, trays, or sometimes casing materials to control contamination. Still, direct use of the substrate can be toxic, unsafe, and may leave harmful residues. Research literature also notes that formaldehyde exposure and residues are a health concern because formaldehyde is a toxic and potentially carcinogenic chemical. Safer and commonly recommended substrate preparation methods include pasteurisation, steam treatment, hot water treatment, or lime treatment, which help reduce contamination without adding toxic chemicals to the growing material.