NFPA 704 Rating System: How a Chemical Gets Its Numbers

Last Updated: 2026-10-14

Answer Capsule: The NFPA 704 rating system assigns each material a health, flammability and instability number from 0 to 4, plus a special hazard symbol. NFPA publishes the criteria, but the facility owner or operator assigns the ratings from each product's Safety Data Sheet. When several chemicals share a room, the placard shows the highest number in each color plus every symbol.

You searched for the NFPA rating of a chemical and found three different answers. One chart says diesel is 0-2-0, your supplier's SDS says 1-2-0, and a sign vendor sells a 2-2-0. Now you have to pick one, put it on the door, and defend it to the fire marshal.

The confusion clears up once you understand how the NFPA 704 rating system actually works. NFPA does not rate chemicals. It publishes criteria, and the person who applies them to the product on your shelf is you.

This post explains who assigns NFPA ratings, what data feeds each number, and why suppliers disagree. It also covers the worst-case rule for a room with more than one chemical. Print Pro AZ works out these ratings from customer inventory lists every week, and Brent Hanke has seen every way the numbers go wrong.

Who Assigns NFPA 704 Ratings?

The facility owner or operator assigns NFPA 704 ratings. Not NFPA, not the fire department, and not the sign company. NFPA 704, the Standard System for the Identification of the Hazards of Materials for Emergency Response, gives the criteria for each number. Applying them to your materials is your job.

This surprises people. They expect NFPA to keep a master list with one official rating per chemical. It does not. The standard describes what a 3 means in each color. A chemical manufacturer's toxicologist reads the product data against that description and prints a rating on the SDS, usually in Section 16. You, as the operator, adopt that rating or work one out yourself from the SDS data.

The fire marshal (the AHJ, or authority having jurisdiction) can question your rating, and some do. What they want to see is a paper trail: this placard says 3-0-1 because these SDS sheets say so. Keep the sheets with your placard order. The reading side of the sign is covered in the NFPA 704 diamond explained guide.

What Data Feeds Each NFPA Rating?

Each NFPA rating comes from a specific part of the Safety Data Sheet. The fastest path is Section 16, which often lists the NFPA rating outright. When Section 16 is silent, you build the rating from four other sections. The SDS format itself comes from OSHA's Hazard Communication Standard, 29 CFR 1910.1200.

Quadrant	SDS section	What you are looking for
Blue, health	Section 11, toxicological information	How badly a short exposure injures a person, matched to the 0 to 4 health criteria
Red, flammability	Section 9, physical and chemical properties	Flash point and boiling point, matched to the flammability bands
Yellow, instability	Section 10, stability and reactivity	Detonation, explosive decomposition, or violent reaction with water
White, special	Sections 5 and 9	Water reactivity (W with a line), oxidizer (OX), or one of the seven SA gases

Flammability is the easiest number because it is tied to a measurement. A flash point below 73 F with a boiling point at or above 100 F is a red 3. A flash point from 100 F to 200 F is a red 2. Gasoline flashes at about minus 45 F, so it is a 3. Diesel flashes at 125 F or higher, so it is a 2.

Health is the hardest because the criteria are written in words. "Short exposure could cause serious temporary or moderate residual injury" is a 3. "Exposure would cause irritation with only minor residual injury" is a 1. Two toxicologists can read the same data and land one number apart.

Callout: Never copy GHS category numbers into the diamond. GHS Category 1 is the most severe, and NFPA 1 is the least severe. A direct copy comes out backwards. The step-by-step SDS method is in the NFPA 704 ratings from a Safety Data Sheet post.

Why Do Suppliers Give Different NFPA Ratings for the Same Chemical?

Suppliers give different NFPA ratings for the same chemical because the product is not always the same. The health and instability criteria also leave room for judgment. Concentration, purity, additives and the person reading the criteria all move the number.

Here are common cases from the Print Pro AZ 50-chemical field guide where sheets differ:

• Diesel: 0-2-0 on most sheets, 1-2-0 or 2-2-0 on others. Same red 2 every time, because flash point is measured. The blue moves with additives and the toxicologist's read.
• Propane: 1-4-0 on most sheets, 2-4-0 on some. The Print Pro AZ propane sign is 2-4-0, and a 1-4-0 generic exists.
• Methanol and isopropyl alcohol: 1-3-0 or 2-3-0.
• Hydrogen peroxide: 30 to 35% is 3-0-1-OX on most sheets, while 3% household is 1-0-0. Concentration changes every number.
• Sodium hypochlorite bleach: 2-0-1, with OX on some sheets, and 12% pool bleach often 3-0-1.
• Anhydrous ammonia: 3-1-0 on most sheets, and R-717 refrigeration grade often 3-3-0.

None of these sheets is wrong for the product it describes. The rule is that the SDS for the exact product and concentration you store is the one you use. Print Pro AZ marks these chemicals with an asterisk in the field guide for that reason. If your sheet gives a different number than a chart, the chart loses.

How Do You Rate a Room With More Than One Chemical?

You rate a room with more than one chemical by taking the highest number in each color from any material present. You also include every special symbol from any material. This is the worst-case rule, and it is the part of the NFPA 704 rating system that catches the most people.

The placard does not average. It does not show the most common chemical or the largest container. It shows the single worst blue, the single worst red, the single worst yellow, and all the symbols.

Worked example. A maintenance shop stores these four materials:

1. Gasoline, 1-3-0
2. Sodium hydroxide, 3-0-1
3. Concentrated sulfuric acid, 3-0-2 with W
4. Calcium hypochlorite pool shock, 3-0-2 with OX

The room placard reads 3-3-2 with both W and OX. Blue 3 comes from the caustic, the acid and the pool shock. Red 3 comes from the gasoline alone.

Yellow 2 comes from the acid and the pool shock. Both symbols appear because each is present somewhere in the room.

Here is a call Print Pro AZ gets every month. A warehouse posted the gasoline diamond on the door because gasoline was the biggest volume in the room. The fire marshal flagged it, because the acid in the corner made the room a blue 3 with a W. The fix was one new placard and a copy of each SDS in the binder.

What Should You Do Once You Have the Numbers?

Once you have the numbers, you order a placard that shows the room rating, sized for the viewing distance. Keep the SDS sheets that back it up. The placard goes at each entrance to the area and on stationary tanks per IFC Section 5003.5. NFPA 704 Table 9.1 sets the size by viewing distance.

Print Pro AZ prints the diamond in 3, 9, 11, 15, 20 and 24 inch sizes. Vinyl goes on indoor cabinets and doors, and .040 rust-free aluminum goes outdoors. If you would rather not work the ratings out yourself, send your chemical inventory as a PDF, Excel or CSV file through the commercial jobs page. Print Pro AZ returns the full placard set with the composite room rating worked out.

Grab the free NFPA 704 Diamond Field Guide with the download form on this page. It lists the ratings of 50 common chemicals with part numbers.

Frequently Asked Questions

Who assigns NFPA ratings?

The facility owner or operator assigns NFPA 704 ratings. NFPA publishes the criteria for each number. Chemical suppliers often print a rating in Section 16 of the SDS, and the operator adopts or verifies that rating for the placard. The fire marshal can question it, so keep the SDS sheets.

Where do I find the NFPA rating on an SDS?

Check Section 16 first, where many suppliers list the NFPA rating outright. If it is missing, use Section 11 for health and the flash point in Section 9 for flammability. Section 10 gives instability, and Sections 5 and 9 give special hazards.

Why does my SDS show a different NFPA rating than the chart?

Because the product, concentration or supplier judgment differs. Diesel, methanol, propane and bleach commonly carry different numbers on different sheets. The SDS for the exact product you store is the one to use, and a chart is only a starting point.

How do you combine NFPA ratings for a storage room?

Take the highest number in each color from any chemical in the room, and include every special symbol present. A room with gasoline (1-3-0) and sulfuric acid (3-0-2-W) is placarded 3-3-2 with W. The placard shows the worst case, not the average.

Conclusion

The NFPA 704 rating system puts the numbers in your hands: NFPA writes the criteria, the SDS supplies the data, and the facility operator assigns the rating. Flammability follows flash point, health follows the injury wording, and instability follows reactivity data. A shared room takes the highest number in each color plus every symbol present.

Getting the rating right the first time saves you a failed fire inspection and a re-print. Partner companies report 45%+ better first-time inspection pass rates.

Shop NFPA 704 diamond signs in any rating, or send your inventory list to Print Pro AZ and let Brent work out the room rating: (602) 649-5305.

Sources

• NFPA 704, Standard System for the Identification of the Hazards of Materials for Emergency Response
• OSHA 29 CFR 1910.1200, Hazard Communication (Safety Data Sheet sections)

Brent Hanke | Print Pro AZ | (602) 649-5305 | b.hanke@printproaz.com

Brent Hanke is the founder of Print Pro AZ, supplying NEC-compliant labels to contractors across the country.