Caution Signs and Warning Signs


Caution signs are required to be posted at the entrance to a space where hazardous materials are stored or used. The caution sign alerts emergency responders and visitors of potential hazards and precautions for entry.

Warning signs alert personnel and visitors to health and safety hazards beyond those identified in the caution sign. Specific warning signs may be required based on the type of hazard present.

Caution signs

Laboratories, shops and maker spaces where hazardous materials are used or stored are required to post an up-to-date caution sign at the entrance.

A caution sign is required to be posted in a Plexiglas holder above or near the room number placard at each entrance that has a door or barrier.

The purpose of the sign is to warn emergency responders and visitors of potential hazards in the space and to meet multiple regulatory requirements. The caution sign consolidates signage requirements for National Fire Protection Association (NFPA) 704 Hazardous Materials, biohazardous and radioactive materials authorization, entry requirements, food and drink prohibitions and lab contact information.

Hazards listed for that location include all items inventoried in MyChem, the University’s chemical inventory database.

The signs are printed out and updated by personnel using the Caution Sign page in MyChem. It is the responsibility of personnel (responsible party, supervisor, manager, etc.) to update the signs if significant changes occur in chemical inventories, entry requirements, hazardous materials authorizations or contacts.

  • Occupants replace signs as needed by updating their MyChem inventory and using the Caution Signs page available in the MyChem menu to print a new sign.
  • You must have an account in the MyChem chemical inventory system to create or edit a sign based on the chemical inventory in your laboratory, shop or maker space.
  • After logging into MyChem, click on the Caution Sign menu item and select the building and room (or suite) to create a customized sign for your location.

Sign holders are provided by EH&S and available upon request by emailing

In addition to the chemical hazards listed under the NFPA diamond, hazards identified on caution signs with pictograms include:

  • Biohazards
  • Compressed gases
  • Cryogens
  • Lead
  • Radioactive materials

Use the Caution Signs Instructions to create and post your caution sign, including:

  • There are two kinds of caution signs – Room Signs and Suite Signs
  • For areas or rooms with multiple entrances – caution signs must be posted at each entrance and show the same information.
  • Look for rooms within a room or rooms accessible only from another room. A collection of rooms like this is considered to be a suite and needs a Suite Sign posted at each main/primary entrance, with Room Signs posted at the entrances of the inner rooms.
  • Within a suite, only rooms that have a door and are used as lab spaces need a Room Sign.
  • Any rooms which are not used for chemical or wet lab work but are still lab spaces (procedure room, microscope room, autoclave room, etc.) should have a caution sign, even if the chemical diamond shows only zeros and no PPE is required.
  • Alcove spaces, open benches, and corridors within a suite that are identified with a room number do not get their own Room Sign. Their inventories are combined into and reflected on the Suite Sign for the suite they are part of via the Caution Sign Tool.
  • All labs that have spaces/alcoves/corridors/inner rooms which are part of a suite must identify each space/alcove/corridor/inner room by room number on the Suite Sign for that suite.
  • Suites within a suite will not be listed on the same caution signs.

Note: All chemicals, compressed gases, and compressed air tanks should be listed in MyChem under the room number that corresponds with their exact location, regardless if that room has its own caution sign. This applies to chemicals and compressed gas tanks located in rooms without doors, alcoves, open benches, and corridors.

An example map of caution sign locations is shown in the Caution Sign Instructions.

Understanding the NFPA Hazard Diamond

The hazard diamond on the caution sign uses a color-coded system with numbers to signal the degree of health hazard (blue), flammability hazard (red), and instability hazard (yellow).

NFPA 704 example


The color-coded number system was developed by the National Fire Protection Association (NFPA).

Flammability, health, and instability

Brief descriptions of the rating numbers for the flammability, health, and instability sections are given in the table below. Numbers in these sections can range from zero to four, with zero meaning essentially no hazard and four indicating an extreme hazard.

These numbers will appear on your caution sign if your inventory contains amounts in the quantities that require a fire permit. You may have chemicals in your lab, shop or maker space, but show zeros on your NFPA diamond if the quantities do not meet or exceed the permit quantities.

Specific hazards

The bottom diamond segment is white and it shows specific hazard codes that identify special problems or require special fire-fighting techniques. These specific hazards include OX (oxidizers), COR (corrosive materials) and W (use no water to fight fires).

The numeric ratings on the colored sections of the diamond on your caution sign are based on the hazard category and the quantity of material as recorded in your MyChem inventory.

Refer to the Table of NFPA codes and Permit Quantities for more information.


explanation of hazard categories

Warning signs

Warning sign(s) may be required to be posted in the area where a potential hazard is present, including biohazards, compressed gases, lasers, lead, liquid nitrogen, magnetic fields, radioactive materials, ultraviolet lights and x-rays.

Spill and exposure response posters

Post the Spill Response Poster and Exposure Response Poster (as applicable) in your workspace for quick reference in case of a hazardous material spill, release or exposure.

Services available

Sign holders for caution signs are provided by EH&S and available upon request by emailing

Please read the FAQ section below or contact EH&S if you have questions about creating a caution sign.

EH&S is available for consultation on selecting the appropriate warning signs for the specific hazards in your work area.

Frequently Asked Questions (FAQ)

The International Fire Code and some other regulations stipulate posting of warning signs under certain conditions. For detailed information, see the links listed under regulation and policy section of this page.

  • Emergency responders (police, fire, medical, spill response)

  • Visitors (vendors, contractors, students, and colleagues from other institutions)

  • UW authorized personnel such as EH&S staff, facilities services and custodial staff

  • General public who may pass by lab/shop

Any UW laboratory, shop or maker space where hazardous materials are used and/or stored is required to have a caution sign.

Labs, shops and maker spaces that have only computers or mechanical equipment (and no chemicals) would not need a caution sign. In this case, you may choose to have a caution sign to indicate that no chemical hazards are present and to display contact information and the “No Food or Drink” image.


The fire diamond provides a quick reference for emergency responders about materials in a room that may present health, flammability, instability, or special hazards under conditions of fire, spill, or similar emergencies.

You may not have enough flammable liquids to warrant the flammability rating. You need to have five gallons total (threshold quantity requiring a Seattle Fire Department permit) of certain classes of flammable liquids to require a number in the red diamond on your sign. See the Table of NFPA Codes and Permit Quantities  for the threshold quantities for each hazard category.

Alternatively, your MyChem inventory may be inaccurate. MyChem performs calculations using your MyChem inventory to determine the numeric hazard ratings for the diamond, so if your inventory is inaccurate, your sign will be inaccurate.

If you have an account in MyChem, the UW online chemical inventory system, you can make a sign for any of the rooms for which you have authorization. Click on ”Caution Sign” under the reports menu to begin creating your sign.

If you need a caution sign holder, contact EH&S at

Contact EH&S at or 206.616.4046.

One name is required for the sign although it will accommodate up to four contacts. After-hours phone numbers are strongly recommended but not required. A department contact such as an administrator is recommended for general information. Lab, shop or maker space contacts are recommended for emergencies and entry after normal business hours. A home phone number, cell phone number or 9-1-1 may be typed in "After Hours Phone" column. Home phone numbers can be added or modifed under the menu item My Contacts.

EH&S installs acrylic holders, usually near the room number plaque. If no holder is outside your door, please contact EH&S at 206.616.5530.

The principal investigator, safety coordinator or their authorized designee.

Generally "authorized personnel" means:

  • Anyone assigned to work in the space

  • Anyone who has been specifically authorized to enter the space

  • UW personnel who, as a part of their responsibility, provide services to spaces such as Facilities Services staff, custodians, EH&S staff and UW Police

  • Labs and shops may restrict entry to protect staff or protect their research and require entry by permission only

The principal investigator, safety coordinator or their authorized designee.

While we can’t name all the regulatory required signs that are not covered by this sign, there are a few common ones that were purposely omitted primarily because they are too complex or variable and require separate signs.

Examples include:

  • Laser warnings
  • UV light hazards
  • Strong magnets
  • Radiation signs for X-ray and high radiation hazards
  • Biosafety Level 2 and 3 signs restricting access while work is in progress
  • Microwave radiation signs

The biohazard symbol on the caution sign indicates that the lab, shop or maker space is authorized at the BSL-1, BSL-2, or BSL-3 level.

If biohazardous materials are present and being manipulated in the lab, shop or maker space, additional sign with more information is required to be posted on the door. For more information, please visit the Biological Research Safety page.

If you have any compressed gas cylinders in your lab, shop or maker space (and it is listed in your MyChem inventory) the compressed gas symbol will appear on your sign. However, compressed gases will only be listed under the NFPA fire diamond if they meet the permit threshold quantities. See the Table of NFPA Codes and Permit Quantities for more information.

Check to make sure the gases are entered in your MyChem inventory. Your compressed gases need to be entered in MyChem in order for the symbol to appear on your sign.

The best way to remove a sign from the holder is to stick the sticky side of a piece of 'post-it' note paper between the plexiglass and the paper sign, so the sticky part is touching the paper sign. Push on the outside of the plexiglass to stick the post-it to the paper sign and slowly pull on the post-it. The sign should slide right out.

More Information


Lab Safety Team Contact

(206) 685-3993
Reference Files