Nitro fuel hazards, as NIOSH and the HSE describe them.

Two chemicals, kept apart

RC nitro fuel is a blend, and the rule books set what may go into it. At IFMAR World Championships, for example, the 1/8 IC off-road rules (2024, section 2.7) and the 1/8 IC track rules (2023, rule 5.23) allow methanol and/or ethanol, lubricating oil, a small amount of anti-corrosion chemicals and at most 25 percent nitromethane by volume, while the 1/10 IC track rules (2024, rule 5.22.1) allow at most 16 percent. The 1/8 off-road rules expressly ban additives including hydrazine, hydrogen peroxide, toluene and propylene oxide. The fuel limits in the rule books read for this site, and the European Union's nitromethane restriction, are on nitro fuel rules.

The two named chemicals carry different hazard ratings, so this page gives each separately and never as a single "nitro fuel" rating. The exposure limits quoted are occupational limits set for workplaces, stated by the agencies; they are not guidance for hobby use.

Methanol, as NIOSH describes it

Fire

The NIOSH Pocket Guide entry for methyl alcohol (CAS 67-56-1, also listed as methanol and wood alcohol) describes a colourless liquid with a pungent smell and classes it as a Class IB flammable liquid, with explosive limits of 6.0 to 36 percent in air. It lists strong oxidisers as incompatible. NIOSH's emergency response card for methanol calls it highly flammable and easily ignited by heat, sparks or flames, says its vapour-air mixtures are explosive, and says the vapour is heavier than air and can travel to a source of ignition and flash back. The card adds that methanol reacts violently with strong oxidants and that containers may explode when heated.

A flash-point disagreement inside NIOSH. The Pocket Guide gives methanol's flash point as 52 degrees Fahrenheit; the emergency response card gives 54 degrees Fahrenheit (12 degrees Celsius). Both are NIOSH documents, and neither figure is preferred here.

Toxicity and the eyes

The Pocket Guide lists the routes of exposure as breathing, absorption through the skin, swallowing, and contact with the skin or eyes. Its target organs are the eyes, skin, respiratory system, central nervous system and digestive tract, and its listed symptoms run from irritation of the eyes, skin and upper airways, headache, drowsiness, dizziness, nausea and vomiting to visual disturbance and damage to the optic nerve, which it describes as blindness.

The emergency response card says swallowing is the most important route of exposure, but that in industry, breathing high vapour concentrations or absorbing methanol through the skin can be as toxic as swallowing it, and that the smell does not reliably warn of low-level exposure. It says symptoms can be delayed by 1 to 72 hours, that the toxicity comes from substances the body makes from methanol, and that these can cause metabolic acidosis, blindness and death. It names the eyes and vision, from blurred sight to partial or total loss, among the targets, lists permanent optic nerve damage among possible long-term effects of severe poisoning, and says developmental toxicity is suspected. NIOSH's archived methyl alcohol topic page says methanol is poisonous, can be absorbed through the eyes, skin, lungs and digestive system, and that overexposure can cause death.

Flames that are hard to see

One point made about methanol is that its flames are hard to see in daylight. The research for this site found it in one place only: a trade-press report (1st Responder News, 27 April 2026) on the Hogansburg Akwesasne Volunteer Fire Department, which serves as the safety team at a full-size racing circuit in New York and is reported as saying methanol can produce almost undetectable flames in daylight. That is a full-size racing context, not an RC source, and the NIOSH card read for this page does not address flame visibility, so the point rests on that single fire-service report.

Nitromethane, as NIOSH and the HSE describe it

NIOSH

The NIOSH Pocket Guide entry for nitromethane (CAS 75-52-5) describes a colourless, oily liquid with a disagreeable smell and classes it as a Class IC flammable liquid with a flash point of 95 degrees Fahrenheit and a lower explosive limit of 7.3 percent; no upper limit is given. It lists as incompatible amines, strong acids, alkalis and oxidisers, hydrocarbons and other combustible materials, and metallic oxides, and notes that it slowly corrodes steel and copper when wet. Its exposure routes are breathing, swallowing and contact with the skin or eyes; its target organs are the eyes, skin, central nervous system and liver. The symptoms it lists are dermatitis and, in animals, eye and respiratory irritation, convulsions, narcosis and liver damage.

The HSE's March 2026 report

The HSE, acting as Great Britain's CLP Agency, published a technical report on the classification and labelling of nitromethane dated March 2026. It concludes that nitromethane meets the criteria for Acute Toxicity 4 (harmful if swallowed and harmful if inhaled), STOT RE 2 (may damage the respiratory tract and nervous system through prolonged or repeated exposure), Carcinogenicity 1B (may cause cancer) and Reproductive Toxicity 1B (may damage the unborn child).

Three points about the report matter for how it is read:

• It agrees with the EU's risk committee. The HSE says its conclusion matches the opinion of the European Chemicals Agency's Committee for Risk Assessment (RAC). The original dossier had proposed a stricter inhalation category, which RAC and the HSE set at Acute Toxicity 4 instead.
• It is not yet adopted in Great Britain. At publication, the report says, this mandatory classification had not yet been agreed or adopted in GB.
• Flammability was kept, not reassessed. Nitromethane's existing GB classification includes Flammable Liquid 3 (flammable liquid and vapour), which the report did not reassess and says should be retained; physical hazards were outside its scope.

The two side by side

IDLH is NIOSH's "immediately dangerous to life or health" concentration. The OSHA figures above are as the NIOSH Pocket Guide gives them; OSHA's own pages were not read. Case reports of people who swallowed model-engine fuel are on injury data.