The short answer
Mineral oil is not flammable. It is combustible. The difference is not pedantry — it decides which storage code applies, what your insurer expects to see, and how the liquid is classified on its safety data sheet.
Flash points for commercial mineral oils run from roughly 135 °C for the lightest grades to over 300 °C for heavy ones. Every one of those numbers sits well above the thresholds that define a flammable liquid. So mineral oil will not flash from a spark at room temperature the way petrol or acetone will — but heat it enough, or soak a wick in it, and it burns steadily and is hard to put out.
Flammable and combustible are not the same word
Both schemes that matter draw the line using flash point — the lowest temperature at which a liquid gives off enough vapour to form an ignitable mixture with air at its surface. Below the flash point there is not enough vapour to light, no matter what you put near it.
Under GHS, flammable liquids are those with a flash point at or below 93 °C, split across four categories, with Category 1 the most hazardous. The European CLP regulation adopts only Categories 1 to 3, so in the EU the practical cut-off is 60 °C. Mineral oil is outside both.
Under NFPA 30, the code used for storage in the United States, the split is at 100 °F (37.8 °C):
| NFPA 30 class | Flash point | Examples |
|---|---|---|
| Class I — flammable | Below 37.8 °C | Petrol, acetone, ethanol, toluene |
| Class II — combustible | 37.8 to below 60 °C | Diesel, kerosene, some white spirits |
| Class IIIA — combustible | 60 to below 93.3 °C | Heavier fuel oils, some plasticisers |
| Class IIIB — combustible | 93.3 °C and above | Mineral oil, most lubricating oils, glycerine |
Mineral oil sits in Class IIIB, the lowest-hazard liquid class in the code. That materially reduces what is required for storage — but Class IIIB is still a combustible liquid classification, not an exemption from one.
Flash points by grade
Flash point tracks viscosity: the heavier the oil, the less volatile it is and the higher it flashes.
| Grade | Typical viscosity (40 °C) | Typical flash point | Typical use |
|---|---|---|---|
| Light white mineral oil | 7–15 cSt | 135–190 °C | Cosmetics, baby oil, textile lubricants, agricultural spray oils |
| Medium white mineral oil | 15–45 cSt | 190–230 °C | Pharmaceutical liquid paraffin, food machinery lubricants, plasticisers |
| Heavy white mineral oil | 45–100 cSt | 230–300 °C | Rubber and polymer processing, heavy textile oils |
| Technical white oil | Wide range | 190–300+ °C | Process oils, release agents, ink oils |
Two cautions when reading a certificate. First, the test method changes the number: Cleveland open cup (ASTM D92) typically reads higher than Pensky-Martens closed cup (ASTM D93) for the same oil, often by 10 to 30 °C. A certificate that gives a flash point without naming the method is incomplete. Second, autoignition temperature is a different property — the temperature at which the oil ignites with no flame or spark present at all. For mineral oils it is typically in the region of 260 to 370 °C. A hot surface above that will light the oil whether or not there is an ignition source.
Where mineral oil does catch fire
“Not flammable” reassures people into three genuine hazards.
- Wicking. Oil absorbed into cloth, lagging, cardboard or porous insulation spreads over a huge surface area. That material ignites far more readily than a pool of oil would, and burns like a lamp wick. Oil-soaked lagging on hot pipework is a classic industrial fire cause.
- Mist and spray. A pressurised leak that atomises the oil produces a fine mist which will ignite well below the bulk flash point — the droplets present the same enormous surface area. Hydraulic and lubrication systems running at pressure near hot surfaces are the standard scenario.
- Oxidisers. Mineral oil in contact with a strong oxidiser — concentrated nitric acid, chlorates, peroxides, permanganates, liquid or high-pressure oxygen — can react violently or ignite without any external heat. This is why oxygen service equipment must never be lubricated with hydrocarbon oil.
On oily rags: the spontaneous combustion risk that makes headlines belongs mainly to drying oils such as linseed and tung, which polymerise and self-heat. Mineral oil does not autoxidise the same way, so the risk is markedly lower — but a heap of oil-soaked rags in a warm, unventilated corner can still accumulate heat, and any oily rag is an easy target for a stray spark. The correct handling is the same either way: closed metal container, and disposal as oily waste.
Once a mineral oil fire has started it behaves like any hydrocarbon pool fire. Water in a jet will spread it; foam, dry chemical, carbon dioxide or water fog are the appropriate media.
What mineral oil actually is
Mineral oil is a mixture, not a compound. It is a highly refined petroleum distillate consisting of saturated hydrocarbons — paraffins and naphthenes — typically in the C15 to C50 range, from which aromatics and unsaturates have been removed by hydrotreating or solvent refining. There is no single CAS number covering all of it; the number on the certificate depends on the refining route, with 8042-47-5 and 8012-95-1 the ones most often seen for white mineral oil.
The degree of refining defines the grade:
- White mineral oil, pharmacopoeial — meets USP, Ph. Eur. or BP monographs for Mineral Oil or Liquid Paraffin, including the ultraviolet absorbance test that limits polycyclic aromatics. Used in pharmaceuticals, cosmetics and as a laxative.
- Food grade / NSF H1 — registered for incidental food contact; the grade for lubricating machinery in a food plant.
- Technical white oil — refined, but not to pharmacopoeial limits. Used in polymer, textile and general processing.
- Process and extender oils — less refined, used in rubber compounding and as plasticisers, and subject to aromatic-content restrictions in several markets.
Note that “liquid paraffin”, “paraffinum liquidum” and “white oil” all refer to the pharmacopoeial or near-pharmacopoeial grades of the same material.
Storage, segregation and firefighting
- Bunding. Store in a bunded area sized to hold the largest container plus a margin. Class IIIB status lowers the fire requirement, not the spill requirement.
- Segregation. Keep well away from strong oxidisers. This is the incompatibility that turns a low-hazard liquid into a serious one.
- Temperature. Keep below 40 °C and out of direct sun. Prolonged heat darkens the oil and raises the acid number.
- Hot surfaces. Route oil lines away from steam pipes and heaters, and repair leaks that can drip or spray onto them. Never leave oil-soaked lagging in service.
- Housekeeping. Oily rags and used absorbent into closed metal containers, emptied regularly.
- Containers. Mild steel drums, HDPE drums, IBCs and ISO tanks are all normal. Keep pharmaceutical and food grades in dedicated, previously unused packing and require a certificate confirming it.
- Firefighting. Foam, dry chemical, carbon dioxide or water fog. Not a straight water jet.
Transport classification and documents
Mineral oil is not assigned a UN number as a flammable liquid and normally moves as general cargo under IMDG, IATA and road regulations. No dangerous goods declaration, no hazard label, no segregation requirement — which is a real commercial advantage over solvent-based alternatives, both in freight cost and in the range of carriers that will take it.
A mineral oil export consignment should still carry a batch-specific certificate of analysis giving viscosity, flash point with the test method named, colour, and for pharmacopoeial grades the monograph tests including the ultraviolet absorbance limit; a 16-section GHS safety data sheet; commercial invoice and packing list; certificate of origin; and, for pharmaceutical, cosmetic or food grades, the declarations the destination requires — typically Halal, Kosher, allergen, BSE/TSE-free, and a food-contact or NSF registration statement.
Writing a specification that gets the right grade
Six things turn a mineral oil enquiry into a firm quotation:
- Grade and standard — USP, Ph. Eur., BP, NSF H1, technical, or your own specification sheet.
- Viscosity — in cSt at 40 °C, with the acceptance range. This is the primary selection variable and the one most often left out.
- Flash point minimum — and the test method you want it measured by.
- Colour and odour — Saybolt colour for white oils; state if the application needs the oil odourless.
- Additional limits — ultraviolet absorbance for pharmacopoeial grades, aromatic content, pour point for cold destinations, and acid number.
- Quantity, packing and destination — 200 litre drums, IBCs or ISO tank, and whether new, dedicated packing is required for the grade.
Enquire with a specification
White and technical mineral oils are supplied by Scapex Exports from qualified Indian manufacturers across pharmacopoeial, food and technical grades, in the viscosity and flash point range the application calls for, with certificate of analysis, safety data sheet and full export documentation.
Send your grade, standard, viscosity, flash point requirement, quantity and destination, and you will get a quotation against that specification rather than a generic one.
Frequently asked questions
Is mineral oil flammable?
No, not in the regulatory sense. A liquid is classified as flammable under GHS only if its flash point is at or below 93 degrees Celsius, and under the stricter EU CLP scheme only at or below 60 degrees. Mineral oil flash points run from roughly 135 to over 300 degrees Celsius depending on viscosity grade, so it falls outside both. It is correctly described as combustible: it will burn once something else has heated it enough to produce vapour.
What is the flash point of mineral oil?
It depends on the grade. Light white mineral oils typically flash between about 135 and 190 degrees Celsius, medium grades between 190 and 230, and heavy grades above 230, with some technical white oils over 300. The figure is measured by Cleveland open cup or Pensky-Martens closed cup, and the two methods do not give the same number, so always read which method the certificate used.
Can mineral oil-soaked rags catch fire on their own?
Mineral oil itself does not self-heat the way drying oils such as linseed or tung oil do, so spontaneous combustion of mineral-oil rags is far less likely. It is not impossible — a pile of oily rags in a warm space with poor ventilation can still build heat, and any rag holding oil is an easy ignition target for a spark. Store used rags in a closed metal container and dispose of them as oily waste, whichever oil it is.
Is mineral oil a dangerous good for shipping?
Generally no. Mineral oil is not assigned a UN number as a flammable liquid and ships as general cargo by sea, road and air. Individual formulated products containing mineral oil may still be regulated on other grounds, and the safety data sheet for the specific product is what governs.
What class is mineral oil under NFPA 30?
Class IIIB. NFPA 30 defines combustible liquid Class IIIB as a flash point at or above 93.3 degrees Celsius, which is 200 degrees Fahrenheit. That is the lowest-hazard liquid category in the code and it carries the lightest storage requirements, but it is still a combustible liquid and not an unclassified one.
What is mineral oil?
White Mineral Oil (Light Liquid Paraffin) (CAS 8042-47-5) is supplied as a colorless clear liquid. Its main applications include emollient and baby oil base. Scapex Exports exports and supplies it from India in IP/USP grade, with a batch Certificate of Analysis (COA) and MSDS.
What is mineral oil used for?
The main applications of White Mineral Oil (Light Liquid Paraffin) are emollient and baby oil base.
Where can I buy mineral oil?
You can buy White Mineral Oil (Light Liquid Paraffin) from Scapex Exports, an exporter and supplier based in Ahmedabad, India. Send the grade, quantity and destination port with the Request a Quotation button on the product page and we will confirm availability, packing and price, with the COA and MSDS.