Formaldehyde is an air-borne, carcinogenic indoor pollutant. It may cause adverse effects on human health such as irritation of eyes and respiratory system. Shells of hermetia illucens, Black Soldier Flies (BSF) are leftovers when the insects mature from pupae to adults. BSF shells are rich in chitin which can be converted into chitosan by demineralisation and deacetylation. Chitosan and its ammonium salt (chitogel) can remove formaldehyde via condensation of water. In this investigation, Anti-Forma Chitogel of BSF was found to be effective in removing (91.2%) formaldehyde (1:20 by mass) among shells of BSF with different treatments and its efficiency was better than all commercial products tested. Concentration of formaldehyde in the container with deacetylated Anti-Forma Chitogel is 0.54 mg/m3. It removed 74.8% of formaldehyde compared to the control (2.14 mg/m3). Concentration of formaldehyde in the container with Anti-Forma Chitogel without deacetylation is 0.76 mg/m3 . It removed 64.5% of formaldehyde compared to the control (2.14 mg/m3). The Anti-forma Chitogel of BSF was found to be eco-friendly with high formaldehyde removal efficiency when placed in a drawer (removal of 54.8% of in 24 hours), the chamber of a newly renovated room (removal of 84.9% in 30 minutes reducing the conc. of formaldehyde from 0.53 mg/m3 to 0.08 mg/m3; cf. the safety limit of formaldehyde <0.125mg/m3) and drawers of a new wardrobe (removal of 83.7% at 20.2oC in 1 day reducing the conc. of formaldehyde from 0.49 mg/m3 to 0.08 mg/m3 & kept the conc. of drawers below 0.125mg/m3 most of the time over a month when temperature was below 21oC). Conc. of formaldehyde in air-tight boxes (5g of construction adhesive in 9.3 dm3) with air purifiers with and without Anti-forma Chitogel as filter before and after 3 hours was reduced by 44.5% (from 6.25mg/m3 to 3.47mg/m3 ) and 27.7% respectively showing that Anti-forma Chitogel as filter in air purifier outperformed that without by 160%. Besides, anti-forma Chitogel is antibacterial, so it would also kill bacteria when used in air purifiers.