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Chemical safety

Formaldehyde solution (formalin): hazards and COSHH prompts

The standard fixative, and a recognised carcinogen with tight workplace exposure limits.

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Always work from your own safety data sheet. Classification varies with grade, concentration and supplier. Use this page to orient yourself, then assess the task you are actually doing, at the scale you are actually doing it.

Hazard classification

CAS
50-00-0
Formula
CH2O
Molecular weight
30.026
Signal word
Danger

GHS pictograms

CorrosionSkull and crossbonesHealth hazardExclamation markFlameGas cylinder

Hazard statements

  • H220Extremely flammable gas
  • H227Combustible liquid
  • H280Contains gas under pressure; may explode if heated
  • H301Toxic if swallowed
  • H302Harmful if swallowed
  • H311Toxic in contact with skin
  • H314Causes severe skin burns and eye damage
  • H315Causes skin irritation
  • H317May cause an allergic skin reaction
  • H318Causes serious eye damage
  • H319Causes serious eye irritation
  • H330Fatal if inhaled
  • H331Toxic if inhaled
  • H334May cause allergy or asthma symptoms or breathing difficulties if inhaled
  • H341Suspected of causing genetic defects
  • H350May cause cancer
  • H351Suspected of causing cancer
  • H370Causes damage to organs
  • H372Causes damage to organs through prolonged or repeated exposure
  • H401Toxic to aquatic life [Hazardous to the aquatic environment, acute hazard]
  • H402Harmful to aquatic life [Hazardous to the aquatic environment, acute hazard]
  • H412Harmful to aquatic life with long-lasting effects
Precautionary statements (46)
  • P203Obtain, read and follow all safety instructions before use.
  • P210Keep away from heat, hot surfaces, sparks, open flames and other ignition sources. No smoking.
  • P222Do not allow contact with air.
  • P233Keep container tightly closed.
  • P260Do not breathe dust, fume, gas, mist, vapours or spray.
  • P261Avoid breathing dust, fume, gas, mist, vapours or spray.
  • P262Do not get in eyes, on skin, or on clothing.
  • P264Wash hands thoroughly after handling.
  • P264+P265Wash hands thoroughly after handling. Do not touch eyes.
  • P270Do not eat, drink or smoke when using this product.
  • P271Use only outdoors or in a well-ventilated area.
  • P272Contaminated work clothing should not be allowed out of the workplace.
  • P273Avoid release to the environment.
  • P280Wear protective gloves, protective clothing, eye protection and face protection.
  • P284P284
  • P301+P317IF SWALLOWED: Get medical help.
  • P301+P330+P331IF SWALLOWED: Rinse mouth. Do NOT induce vomiting.
  • P301+P316IF SWALLOWED: Get emergency medical help immediately.
  • P302+P352IF ON SKIN: Wash with plenty of water.
  • P302+P361+P354IF ON SKIN: Take off immediately all contaminated clothing. Immediately rinse with water for several minutes.
  • P304+P340IF INHALED: Remove person to fresh air and keep comfortable for breathing.
  • P305+P354+P338IF IN EYES: Immediately rinse with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing.
  • P305+P351+P338IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing.
  • P308+P316IF exposed or concerned: Get emergency medical help immediately.
  • P316Get emergency medical help immediately.
  • P317Get medical help.
  • P318If exposed or concerned, get medical advice.
  • P319Get medical help if you feel unwell.
  • P320P320
  • P321Specific treatment — see the safety data sheet.
  • P330Rinse mouth.
  • P332+P317If skin irritation occurs: Get medical help.
  • P333+P317If skin irritation or rash occurs: Get medical help.
  • P337+P317If eye irritation persists: Get medical help.
  • P342+P316P342+P316
  • P361+P364Take off immediately all contaminated clothing and wash it before reuse.
  • P362+P364Take off contaminated clothing and wash it before reuse.
  • P363Wash contaminated clothing before reuse.
  • P370+P378In case of fire: Use appropriate extinguishing media.
  • P377P377
  • P381P381
  • P403+P233Store in a well-ventilated place. Keep container tightly closed.
  • P403Store in a well-ventilated place.
  • P405Store locked up.
  • P410+P403Protect from sunlight. Store in a well-ventilated place.
  • P501Dispose of contents and container in accordance with local, regional and national regulations.

Classification data from PubChem CID 712 , retrieved automatically and refreshed weekly. PubChem aggregates from multiple suppliers; entries can differ from the SDS for your grade.

What your COSHH assessment has to answer

Based on the hazard classes above. These are prompts, not answers — the right control depends on your task, your quantities and your room.

Because it is flammable

  • Where are the ignition sources relative to where this is opened and poured?
  • How much is on the bench at once, and how much is in the cabinet?
  • Is decanting done in the fume hood, and are larger containers earthed?
  • Which extinguisher is appropriate, and does everyone using this know?

Because it is acutely toxic

  • Which exposure route is credible for your task — inhalation, skin, or both?
  • Is containment engineered (fume hood, cabinet) rather than relying on PPE?
  • What is the first-aid response, and is the material for it actually at the point of use?
  • Is lone working with this restricted?

Because it burns or irritates skin and eyes

  • Is eye protection specified for the actual task, including splash risk when pouring?
  • Are the gloves rated for this substance and this contact time?
  • Where is the nearest eyewash, and when was it last flushed and checked?

Because it is a carcinogen, mutagen or reproductive hazard

  • Has substitution been considered, and is the reason for not substituting recorded?
  • Is exposure reduced as low as reasonably practicable, not merely below a limit?
  • Are new and expectant mothers specifically considered?
  • Is health surveillance or exposure monitoring expected for this work?

Because it can damage organs

  • Is the exposure repeated or long-term rather than one-off?
  • Is there an exposure limit to design the controls around?
  • Are users told what early symptoms look like and who to report them to?

Because it is hazardous to the environment

  • Is drain disposal ruled out, and does everyone know that?
  • Is the waste container labelled at the point of generation?
  • Is the disposal contractor's consignment paperwork in order?

Others in fixatives & biological reagents

Paraformaldehyde

Powder form that depolymerises to formaldehyde — heating to dissolve it is the exposure risk.

Read

Phenol

Present in many nucleic-acid extraction reagents; causes severe burns that can be painless at first.

Read

2-Mercaptoethanol

Reducing agent used in protein and RNA work — acutely toxic and unmistakable by smell.

Read

Stop rebuilding this by hand

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