HMIS Color Bars Explained: Numbers, Colors, and the PPE Letter Codes
The Color Bars You've Seen on Chemical Containers
Look at the side of a paint can, a solvent drum, or a labeled spray bottle in an industrial setting and you'll often see a stack of four colored bars — blue, red, orange, and white — each with a number or letter. That's an HMIS label (Hazardous Materials Identification System), the workplace cousin of the NFPA 704 diamond.
This article explains what every bar, number, asterisk, and PPE letter means, who assigns them, and how HMIS differs from the NFPA 704 diamond you see on storage tanks and building entrances.
Edition note: This article reflects HMIS III, the current version maintained by the American Coatings Association. The biggest change from HMIS II was renaming the yellow "Reactivity" bar to the orange "Physical Hazard" bar and aligning the criteria with the GHS.
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The Four Bars — What Each Color Means
HMIS III stacks four horizontal bars. The top three are hazard ratings; the bottom is about protection.
| Bar | Color | What it rates | Carries |
|---|---|---|---|
| Health | 🟦 Blue | Acute (and, with an asterisk, chronic) health effects | A number 0–4 |
| Flammability | 🟥 Red | How easily it ignites (flash point + boiling point) | A number 0–4 |
| Physical Hazard | 🟧 Orange | Reactivity, instability, water reactivity, explosivity | A number 0–4 |
| Personal Protection | ⬜ White | The PPE the worker must wear | A letter (A–K, or X) |
The three hazard bars use the same 0 to 4 scale — higher means more dangerous. The white bar is different: it carries a letter that maps to a specific PPE set.
The Numbers — 0 to 4 Decoded
Blue (Health)
| Rating | Meaning |
|---|---|
| 0 | Minimal hazard; no significant risk to health |
| 1 | Slight hazard; minor reversible injury possible |
| 2 | Moderate hazard; temporary or minor injury may occur |
| 3 | Serious hazard; major injury likely without prompt treatment |
| 4 | Severe hazard; life-threatening, major or permanent damage |
Red (Flammability)
The flammability criteria are essentially identical to NFPA 704 — based on flash point and boiling point.
| Rating | Meaning |
|---|---|
| 0 | Will not burn under typical conditions |
| 1 | Must be preheated before ignition (flash point > 200°F) |
| 2 | Must be moderately heated; flash point 100–200°F |
| 3 | Ignites under most ambient conditions; flash point < 100°F |
| 4 | Extremely flammable; flash point < 73°F and low boiling point |
Orange (Physical Hazard)
In HMIS III the orange bar replaced the older yellow "Reactivity" bar. It covers reactivity, instability, water reactivity, organic peroxides, pyrophorics, and explosivity.
| Rating | Meaning |
|---|---|
| 0 | Stable; not reactive, even under fire conditions |
| 1 | Normally stable; may become unstable at elevated temperature/pressure |
| 2 | Unstable; may react violently or form explosive mixtures |
| 3 | May detonate or explode with a strong initiating source |
| 4 | Readily detonates or explodes at normal temperature/pressure |
The Asterisk (*) — The Chronic-Hazard Flag
The single most misunderstood mark on an HMIS label is the asterisk next to the Health number.
An asterisk means the chemical poses a chronic (long-term) health hazard — a carcinogen, mutagen, reproductive toxin, or respiratory sensitizer — where the danger comes from repeated or prolonged exposure, not a single acute dose. A "2*" tells a worker: it's moderately hazardous today, but it can also hurt you slowly over months or years.
NFPA 704 has no chronic-hazard indicator at all — this is one of the practical reasons facilities choose HMIS for in-house worker labeling.
The PPE Letter Codes — A Through K (and X)
The white Personal Protection bar is HMIS's signature feature and has no NFPA 704 equivalent. Instead of a number, it carries a letter that maps to a defined PPE set:
| Letter | Required PPE |
|---|---|
| A | Safety glasses |
| B | Safety glasses, gloves |
| C | Safety glasses, gloves, apron |
| D | Face shield, gloves, apron |
| E | Safety glasses, gloves, dust respirator |
| F | Safety glasses, gloves, apron, dust respirator |
| G | Safety glasses, gloves, vapor respirator |
| H | Splash goggles, gloves, apron, vapor respirator |
| I | Safety glasses, gloves, dust & vapor respirator |
| J | Splash goggles, gloves, apron, dust & vapor respirator |
| K | Airline hood or mask, gloves, full suit, boots |
| X | Consult your supervisor or specialist — special handling |
Important: the employer assigns the PPE letter, not the chemical manufacturer. The letter reflects how the chemical is actually used at *your* site — the same product can warrant a different code in a lab versus a high-volume production line. The three hazard ratings come from the SDS; the PPE letter is a site-specific decision.
HMIS vs. NFPA 704 — Side by Side
They look like cousins, and they are — but they're built for different people.
| HMIS III | NFPA 704 | |
|---|---|---|
| Audience | Workers handling the chemical | Emergency responders arriving on scene |
| Shape | Horizontal color bars | Four-quadrant diamond |
| Health | Blue + chronic asterisk | Blue (no chronic marker) |
| Flammability | Red | Red |
| Third bar | Orange "Physical Hazard" | Yellow "Reactivity/Instability" |
| PPE | Letter code A–K, X | None |
| Special hazards | Captured in Physical Hazard rating | White quadrant (W, OX, SA) |
| Required by OSHA? | No (proprietary; accepted for workplace labels) | No (but adopted by many fire codes) |
Need the diamond instead? Use the free NFPA 704 Diamond Generator.
Is HMIS Required? Where It Fits With OSHA
HMIS is not required by any OSHA standard — it's a proprietary system owned by the American Coatings Association. But OSHA's Hazard Communication Standard, 29 CFR 1910.1200(f)(6), requires that workplace (secondary) containers carry the product identifier plus "words, pictures, symbols, or combination thereof" giving general hazard information.
An HMIS color bar is an accepted way to satisfy that workplace-labeling requirement — as long as your employees are trained on what the bars, numbers, asterisk, and PPE letters mean, and your Safety Data Sheets stay accessible. HMIS does not satisfy primary container labeling (1910.1200(f)(1)), which requires the full GHS format with pictograms, signal word, and hazard statements. For those, use the free GHS Label Generator.
Generate a Compliant HMIS Label in Seconds
You don't need a sticker catalog or a design tool. Our free HMIS Color-Bar Label Generator lets you set the Health, Flammability, and Physical Hazard ratings, flag a chronic hazard, pick the PPE letter, and download a print-ready PDF — no account, no payment.
And if you're labeling more than a handful of chemicals, Tellus auto-generates HMIS, NFPA, and GHS labels for every chemical in your inventory straight from your uploaded SDSs, prints them in batch, and keeps them current as revisions roll in.