Does a Fragrance Oil's Flash Point Matter?

A fragrance oil's flash point is the temperature at which its vapor can ignite if it meets a flame or spark. It matters for fire safety, for shipping, and for some candle types such as gel. It does not tell you when your scent will burn off. Look it up on the oil's safety data sheet, keep open flames and sparks away while you work, and test your wax, oil and wick in your own jar.

What is a flash point, exactly?

OSHA's rule defines it as the minimum temperature at which a liquid gives off enough vapor to form an ignitable mixture with air near its surface. CandleScience defines it as the temperature at which a fragrance or essential oil can ignite from an open flame or spark. Supplies for Candles (UK) says heat alone does not cause ignition, the flame or spark does. That is about the flash point only, and it does not mean hot wax can never catch: Lone Star says overheated wax can become a fire hazard. Craftybase says it is a safety threshold, not a point where the oil bursts into flame on its own.

The number is on each oil's safety data sheet, which suppliers keep with the product page. CandleScience's page says it is not a concern at room temperature.

What does it not mean?

It does not mean your fragrance "burns off" at that temperature. Supplies for Candles says oils do not burn off in normal candle making, and links scent loss to boiling point instead. CandleScience says low flash point fragrances do not burn off when added to wax and poured promptly. Craftybase makes a different scent argument, that wax too hot drives off the lighter top notes. That is a claim about heat and scent, not about flash point, and I could not check it.

Where does it matter?

• Shipping. CandleScience says oils with a flash point of 141 F or lower cannot go by USPS and must go by ground service, and that all its oils are above 141 F. USPS Publication 52 is the rule itself and is more exact: a liquid with a flash point of 140 F or lower is a flammable liquid, barred from air and international mail and mailable by surface only with limits. Liquids from 140 F to 200 F have their own rules. Check the current rule before you mail oil.
• Gel candles. CandleScience quotes Penreco, a gel wax maker, as recommending fragrances with flash points over 170 F. Supplies for Candles gives above 77 C (170.6 F) for gel and says its gel wax holds up to 6 percent oil.
• Where you sell. Craftybase says many venues and carriers restrict oils with flash points below 170 F. I could not confirm that for any specific venue, so ask the one you sell at.
• At the bench. Lone Star says to keep the oil a safe distance from open flame. A lit gas burner is an open flame, so my cautious advice is to keep the bottle away from it and add oil with the pitcher off the burner.

Should I add oil below its flash point?

The suppliers disagree, and I can only report it. Craftybase says to add at or below the flash point, at least 10 to 15 F under it, and its stated reason is keeping the top notes, not fire. CandleScience says adding oil above its flash point will not cause combustion. Lone Star says it is safe to add above it, away from open flame. Supplies for Candles says wax may be hotter than the flash point while mixing and that the oil will not ignite without an open flame. Voyageur says to adjust your wax temperature if an oil has a lower flash point. Our guide on when to add fragrance sets the numbers side by side.

My own rule is the cautious one. Read the data sheet, know the number, keep flames away, and ask the oil's supplier if it is lower than your wax's add temperature.

Worked example: reading three data sheets

Data sheets give flash points in C and F. The first two are real CandleScience sheets (created 11/2/2020). The third is made up.

• Plumeria: 102 C, listed as 216 F. Check: 102 x 1.8 + 32 = 215.6 F.
• White Sage and Lavender: 100 C, listed as 212 F. Check: 100 x 1.8 + 32 = 212 F.
• Example oil: 140 F, which is (140 - 32) / 1.8 = 60 C.

Against the rules above: both real oils clear the 170 F line by 46 F and 42 F (216 - 170, 212 - 170), though Supplies for Candles also says to use only fragrances recommended for gel. Our example is at 140 F, so USPS would class it as a flammable liquid (surface mail only, with limits), and it is 30 F under the 170 F gel line. Compare the wax. The maker's 2023 EU data sheet for Golden Wax 464 lists the wax's own flash point above 290 C (554 F), so the oil is the lower number in the pitcher. A blend of oils has no number I could find in a source. I use the lowest flash point among the oils as a rough working number, not a measured one, and ask the supplier.

Common mistakes

• Treating the flash point as a scent-loss temperature.
• Never looking at the data sheet.
• Assuming a gel candle can use any oil.
• Using a bottle's flash point from a different oil or a different supplier.
• Leaving the oil bottle open near a burner.

Questions

Does a low flash point mean an oil is unsafe in candles?

I did not find a source that says so. CandleScience says it is not a concern at room temperature and that low flash point oils keep their strength if poured soon. It does change how you handle and ship them, and whether you can use them in gel.

Where is the flash point on my oil?

On its safety data sheet, which suppliers keep on the product page. Supplies for Candles says to look under the technical data sheets tab. Tab names vary by supplier.

Is the oil's flash point the same as the wax's?

No. They are separate numbers on separate sheets. The soy wax data sheets I opened list a flash point far above any pour temperature, while the two oil sheets above list 212 F and 216 F.