Labeling and Marking Systems

Read the label

Always read the labels provided on the products
you use!!!

These will provide you with a wealth of information you need to know in order to use the product safely.

In addition to the manufacturers' labels which are provided on most chemical products, there are three generic three labeling and marking systems:

Hazardous Materials Labeling System (HMLS) labels
National Fire Protection Association (NFPA) diamonds
Uniform Laboratory Hazard Signage (ULHS) system

The first two of these systems rely on color coding and a numerical rating system to identify hazards and their severity. The ULHS system identifies the areas where hazardous substances are used or stored through pictograph symbols.

NFPA Diamonds

Hazardous chemicals will have NFPA diamonds located somewhere on the container and corresponding information on the MSDS.  Each diamond represents a different hazard.

Blue = Health Hazard
Red = Flammability
Yellow = Instability
White = Special Hazard Information

A numerical rating will also be provided in the blue, red, and yellow diamonds. This number indicates the severity of the hazard, with a 0 indicating no hazard and 4 indicating the most severe hazard.

Key to the NFPA Diamond - Click Image to see full view

NFPA Diamond

HMLS Labels

The HMLS labeling system operates on the same principle as the NFPA diamond. Blue indicates health hazard, red indicates flammability, yellow indicates instability, and special information (such as what personal protective equipment to wear) will be provided in the white section. It also uses a numerical system from 0-4 to indicate the severity of the hazard.

Either of these labels could be used on individual containers of hazardous materials (ie. barrels, bottles, cans, buckets, tubs, etc) so that there are never any unlabeled containers in the work area. 

Always regard unlabeled containers as dangerous!

If a product or chemical is removed from its original container into another container which doesn't have a manufacturer's label, the second container must be labeled with an HMLS label with the appropriate information filled out (unless under direct control of the preparer during the same work shift, example diluted lab chemicals for students use during that class). 

HMLS Label

HMIS Label

Key To HMLS and NFPA Label Numerical Rating Systems


4 Deadly: even the slightest exposure to this substance would be life threatening. Only specialized protective clothing, for these materials, should be worn.
3 Extreme Danger: serious injury would result from exposure to this substance. Do not expose any body surface to these materials. Full protective measures should be taken.
2 Dangerous: exposure to this substance would be hazardous to health. Protective measures are indicated.
1 Slight Hazard: irritation or minor injury would result from exposure to this substance. Protective measures are indicated.
0 No Hazard: exposure to this substance offers no significant risk to health.



Flash Point Below 73ºF and Boiling Point Below 100ºF: this substance is very flammable, volatile or explosive depending on its state. Extreme caution should be used in handling or storing of these materials.


Flash Point Below 100ºF: flammable, volatile or explosive under almost all normal temperature conditions. Exercise great caution in storage or handling of these materials.


Flash Point Below 200ºF: moderately heated conditions may ignite this substance. Caution procedures should be employed in handling.


Flash Point Above 200ºF: this substance must be preheated to ignite. Most combustible solids would be in this category.


Will Not Burn: substances that will not burn.



May Detonate: substances that are readily capable of detonation or explosion at normal temperatures and pressures. Evacuate area if exposed to heat or fire.


Explosive: substances that are readily capable of detonation or explosion by a strong initiating source, such as heat, shock or water. Monitor from behind explosion-resistant barriers.


Unstable: violent chemical changes are possible at normal or elevated temperatures and pressures. Potentially violent or explosive reaction may occur when mixed with water. Monitor from a safe distance.


Normally stable: substances that may become unstable at elevated temperatures and pressures or when mixed with water. Approach with caution.


Stable: substances which will remain stable when exposed to heat, pressure or water.

Uniform Laboratory Hazard Signage

Proper signage on door of lab Laboratories and other potentially hazardous areas could be marked with the appropriate pictographic symbols to warn employees, visitors, and emergency responders what precautions should be observed when entering the laboratory, as well as what hazards to expect inside.  The ULHS could be used for this purpose, but it is not necessary.

Some common pictographs labels are available for a variety of hazards such as these:

Biohazard label
Oxidizer Label
Electrical Hazard Label
Cancer Hazard Label

The Four Stages of an effective hazard communication program are:

Material Safety Data Sheets
Labeling and Marking Systems
Employee Training Sessions
Written Right-to-Know Plan


In Maine, the supervisor, facility manager, and/or person responsible for the overall HazCom plan sould be contacted for information with respect to labeling, hazards, and container markings.