How to Read an NFPA 704 Diamond

In One Easy Lesson (In Four Parts)

The NFPA Diamond rating system was developed to enable first responders to a fire or similar emergency to see at a glance what hazards they might encounter while performing their duties. It didn’t take long for employers and chemical workers to realize that the Diamond was a useful tool for them as well. But it only helps if you know how to read it and to understand what it says.


I’m sure that most of you know the basics of reading the Diamond – you know that the blue square carries a Health rating, the red square carries a Flammability rating, and the yellow square carries a Chemical Instability rating. You may or may not know that the fourth square, the white one, is there in case a “Special Hazard” notification is necessary. (More on that later.)

The blue, red, and yellow squares will each have a number between 0 and 4 – the higher the number, the greater the hazard. We’ll discuss the squares individually.


Remembering that the NFPA Diamond system was developed primarily for firefighters will help you understand the Health ratings. For instance, a rating of “0” means that this material, under emergency conditions, would be no more hazardous than an ordinary combustible material. In other words, this substance may burn, but would be no more dangerous than, say, burning paper – yes, you could burn yourself with it, but you won’t be inhaling poisonous fumes.

A rating of “1” in the Health square indicates a material that, “under emergency conditions, can cause significant irritation” of lungs, skin, or eyes, or is somewhat toxic if taken orally. Isopropanol falls into this category.

A Health rating of “2” indicates a material that, “Under emergency conditions, can cause temporary incapacitation” or lasting, but not permanent, injury. Acetone and Kerosene are in this category.

A Health rating of “3” is given to a material that, “under emergency conditions, can cause serious or permanent injury”. Some examples in this category are Acetic Acid, Ammonia, and Carbon Dioxide.

Finally, the highest rating, a ”4” in the Health square, is reserved for  materials that, “under emergency conditions, can be lethal”. Hydrofluoric Acid (HF) is one of these, as is Hydrogen Sulfide.



A Personal History of HCL

When I first started working for HCL Labels, in January of 1980, it was part of a larger company called Safety Specialists, Inc. There were two of us working at HCL, and I was second in command.

We had our office on the second floor of a frontier-style, wooden building in Boulder Creek, California. There were two desks, two typewriters*, two phones with two local lines and two toll-free lines, a coffee maker, and lots and lots of shelves full of ready-to-go, pre-printed HCL Labels and signs. Did you notice that there were twice as many phone lines as employees? Yes, it got hectic at times!

When the phone rang, one or the other of us would answer it and take down the particulars of the order. If the order was for stock labels or signs, we would then count the labels by hand, 25 per box, and enclose them in hinged, rigid plastic snap-close boxes. The boxes would go into a cardboard box, or sometimes a padded envelope, and be shipped off.

If the order was for a custom chemical label, I would pull out my reference books, type out the copy for the label, hand-draw the appropriate pictorial symbols, and mail the paper to our printer in southern California. The printed labels would arrive within 3 – 4 days, after which we would count them into the plastic boxes.

As I write this, even I am amazed at how primitive it sounds! Reference books? A typewriter? Snail mail?! How things have changed! Hope you have enjoyed this glimpse into the past!
*typewriter: a primitive machine for writing. Its arrangement of keys was similar to today’s computer keyboards.

So When Do I Need a GHS Label?

Now that you understand what the cute little pictorials on the new GHS labels mean, you may be wondering when you need to use a GHS label. The answer is pretty simple – you need a GHS label whenever you have a secondary container of a chemical or chemical mixture.

For instance, if you or your employer purchases a five-gallon container of, say, Isopropyl Alcohol for use in the laboratory or workplace, it will come in a container labeled with the required GHS warnings and instructions. Now if you pour some of that isopropyl alcohol into a secondary container, such as a one-pint wash bottle, you have a potentially dangerous situation – a wash bottle full of unidentified liquid that looks like water. So what do you do? Slap a ready-made HCL GHS label for Isopropyl Alcohol on that squeeze bottle and be on your way.

When do you NOT need a GHS label? This is the exception to the rule. You do not need a GHS label on your secondary container if, and only if:

  • The material in the secondary container is entirely used within the work shift of the person who transferred the material to the secondary container, AND
  • The person who transferred the material stays in the work area for the entire time that the material is being used, AND
  • The secondary container stays within the work area and in the possession of the person who transferred the material into it.

Got it? Good!  Go label those secondary containers!