Formaldehyde
CAS 50-00-0 · EC 200-001-8 · CH2O
Also known as formalin (aqueous solution), methanal
Handle chemistry safely
Wear gloves and eye protection, work with good ventilation, and read the supplier’s safety data sheet before use. Hazard information here is a summary, not a replacement for it. Dispose of all photographic chemistry correctly, in line with local laws and your local authority’s guidance. Never mix waste solutions, and check the supplier’s safety data sheet before disposing of anything.
Hazards
Official EU classification (harmonised under CLP Annex VI).
Signal word: Danger
Serious health hazard · Acute toxicity · Corrosive
- H350 May cause cancer.
- H341 Suspected of causing genetic defects.
- H330 Fatal if inhaled.
- H302 Harmful if swallowed.
- H314 Causes severe skin burns and eye damage.
- H317 May cause an allergic skin reaction.
- EUH071 Corrosive to the respiratory tract.
UK and EU rules
- CLP Annex VI Carc. 1B, Muta. 2 – harmonised entry 605-001-00-5 (ATP22)
- REACH Annex XVII entry 77 (formaldehyde and formaldehyde releasers – emission limits for articles – Reg. (EU) 2023/1464)
- UK Poisons Act 1972: reportable poison – formaldehyde 5% w/w
Photographic uses
- hardener (historic)
Sources
- ECHA CHEM substance record: Formaldehyde (100.000.002)
- ECHA CHEM – C&L Inventory (harmonised CLP Annex VI and notified classifications) and legal obligations (chem.echa.europa.eu APIs: /api-cnl-inventory/harmonized|industry, /api-obligation-substance/v1)
- Supplying explosives precursors and poison substances: list of chemicals (supplying-explosives-precursors/list-of-chemicals (updated 3 July 2026))
- REACH Annex XVII entries 28–30 (CMR substances – supply to general public) (Annex XVII entries 28, 29, 30; latest consolidated act CELEX 32025R1731)
Checked October 2026.