Most scented candle labels in the EU carry the word "Warning". Now and then a maker runs the numbers on a wax melt or a reed diffuser and gets "Danger" instead, and wonders whether something went wrong. Usually nothing did. The signal word follows fixed rules in the CLP Regulation, and a few ingredients plus a higher load are enough to move a home fragrance product from one word to the other.

What a signal word is

A signal word tells the reader how serious the most severe hazard on the label is. CLP has only two: "Danger" for the more severe hazard categories and "Warning" for the less severe ones. In Spanish they are «Peligro» and «Atención». The word is not something you choose. It comes out of the product's classification.

Article 20 of CLP sets three rules:

  • The label must include the signal word that matches the classification.
  • Which word goes with which classification is fixed in the label-element tables of Annex I.
  • If "Danger" is on the label, "Warning" must not appear. There is only ever one signal word.

So a label never says "Danger" and "Warning" side by side. The most severe classification wins, and every other hazard statement stays on the label under that one word.

Which classifications carry which word

These are the Annex I assignments for the hazard classes that come up in candles, wax melts and diffusers:

  • Skin Sens. 1, 1A or 1B (H317, allergic skin reaction): Warning, exclamation mark.
  • Skin Irrit. 2 (H315) and Eye Irrit. 2 (H319): Warning, exclamation mark.
  • Eye Dam. 1 (H318, "Causes serious eye damage"): Danger, corrosion pictogram.
  • Asp. Tox. 1 (H304, "May be fatal if swallowed and enters airways"): Danger, health hazard pictogram.
  • Flam. Liq. 3 (H226): Warning. Flam. Liq. 2 (H225): Danger. Both with the flame.
  • Aquatic Chronic 1 (H410): Warning, environment pictogram.
  • Aquatic Chronic 2 (H411): environment pictogram but no signal word.
  • Aquatic Chronic 3 (H412): no signal word and no pictogram.

For a candle, the usual classifications are H317 and one of the aquatic statements, so the word is "Warning" or nothing. "Danger" needs something more serious, and in home fragrance that almost always means serious eye damage, aspiration toxicity or a highly flammable liquid.

Where "Danger" comes from in home fragrance

Eye damage. A mixture is classified Eye Dam. 1 when its ingredients classified Eye Dam. 1 or Skin Corr. 1 add up to 3% or more. From 1% to under 3% it is Eye Irrit. 2 instead, which only needs "Warning". Some common fragrance materials are classified for eye damage by their suppliers. Geraniol is a good example: its harmonised EU entry covers only Skin Sens. 1, but manufacturers commonly self-classify it as Eye Dam. 1 (BASF's own SDS for geraniol, for one, carries H318 and "Danger"). If your fragrance SDS lists an ingredient with H318, its percentage matters.

Aspiration toxicity. A mixture is Asp. Tox. 1 when its Asp. Tox. 1 ingredients add up to 10% or more and its kinematic viscosity is 20.5 mm²/s or less at 40 °C. That is a runny liquid. Isoparaffin solvents used as diffuser bases are typically classified Asp. Tox. 1, and so is d-limonene in its harmonised entry. A reed diffuser liquid can cross 10% easily. A solid candle or wax melt is not a runny liquid at 40 °C, so this route is really a diffuser problem. We cover it in detail in our guide to H304 in home fragrance.

Flammability. Ethanol has a harmonised Flam. Liq. 2 classification. An alcohol-based diffuser is likely to be highly flammable (H225) and therefore "Danger" on that alone.

A worked example: one oil, three products

Take a hypothetical floral fragrance oil whose SDS lists 15% linalool (harmonised Skin Sens. 1B) and 20% geraniol (harmonised Skin Sens. 1, and Eye Dam. 1 on this supplier's SDS). To keep it simple, assume nothing else in the oil is classified.

  • Candle at 10% load. The candle holds 1.5% linalool and 2.0% geraniol. Both are at or above the 1% sensitiser limit, so the candle is H317. Geraniol's 2.0% sits between 1% and 3%, so the candle is Eye Irrit. 2, H319, not Eye Dam. 1. Everything here carries "Warning": one exclamation mark, signal word Warning.
  • Wax melt at 15% load. Now it's 2.25% linalool and 3.0% geraniol. Geraniol reaches the 3% line, so the melt is Eye Dam. 1, H318, with the corrosion pictogram. The label says Danger, and "Warning" disappears. The exclamation mark stays for H317: CLP drops it when the corrosion pictogram is present only if it was there for irritation, not for sensitisation.
  • Same wax melt at 12% load. Geraniol drops to 2.4%, the melt goes back to Eye Irrit. 2, and the word goes back to Warning. With this oil, the line sits at exactly 15% load (3% ÷ 20%).
  • Reed diffuser, 20% oil in an isoparaffin base. The base is 80% of the liquid and classified Asp. Tox. 1, and the liquid is thin, so it is H304. Geraniol is at 4%, so it is also H318. The label carries the health hazard, corrosion and exclamation mark pictograms, and one signal word: Danger.

The same oil gives "Warning" in a candle and "Danger" in a strong wax melt or a diffuser. A real fragrance has more components and needs the full calculation, but this is the mechanism.

When there is no signal word at all

Two common situations leave the signal word off entirely:

  • Only an EUH208 line. Take the same oil at 4% in a candle: 0.6% linalool and 0.8% geraniol. Both are under the 1% limit, so there is no H317, and geraniol is under 1% for eyes. The candle is not classified. Both allergens still go on the EUH208 "Contains… May produce an allergic reaction" line, but EUH208 is supplemental information, not a classification. No pictogram, no signal word.
  • Only H412. Aquatic Chronic 3 is the one classification that comes with neither a pictogram nor a signal word. A candle whose only classification is H412 prints the hazard statement and its precautionary statements, and no "Warning". We explain why in our post on candle hazard pictograms.

H411 alone is the same: the environment pictogram, but no signal word. Add H317 and "Warning" appears, because the sensitiser brings it.

What to check on your own labels

  • Never print both words. If any classification needs "Danger", that's the only word.
  • Don't copy the word from the fragrance SDS. The oil is classified at 100%. Your product is diluted and usually drops to "Warning" or to nothing.
  • Look for H318 and H304 in the SDS. They are the ones that turn a wax melt or a diffuser into "Danger". Check your load against the 3% eye-damage and 10% aspiration lines.
  • Diffusers deserve their own calculation. The base solvent often decides the signal word before the fragrance does.

Molekule reads every component from your fragrance SDS, runs these calculations for your candle, wax melt or reed diffuser, and picks the single signal word the label needs. Check which signal word your product needs in Molekule.