ERG guide number lookup.

How a guide number works

The Emergency Response Guidebook (ERG) is a guidebook for first responders during the initial phase of a transportation incident involving hazardous materials, and PHMSA hosts the 2024 edition. Its orange-bordered section holds one page pair for each guide, and the guide number is the link between a material and the response advice. In the 2024 edition the guides run from 111 to 174. Guides 121 and 167 are printed but marked "Intentionally left blank: There are no materials that refer to this guide." There is no guide 175 in this edition.

You normally reach a guide from an identification number. The ERG tells you to search for the four-digit UN or NA number in the yellow pages, or the material name in the blue pages, and read the guide number next to the entry. If the number is followed by a P, the material may suffer a violent polymerization. If the material is highlighted in green and is not on fire, the flowchart says to use Table 1 for isolation and protective action distances and to consult the orange guide. If it is on fire, use the orange guide for evacuation distances, then protect in the downwind direction according to Table 1 for any residual release. If the entry carries the reference for when spilled in water, consult Table 2 for the generated gases (for information only) and do not use water as the extinguishing agent. The flowchart carries a warning: do not use it if more than one hazardous material is involved. Call the emergency response agency listed inside the back cover instead.

When you only have a placard

The guidebook includes a table of markings, labels and placards for the case where the ID number or shipping name cannot be found. It says to use that table only then, to approach upwind, uphill and upstream at a safe distance, and to match the placard to the circled guide. Examples printed in the guidebook are Guide 127 for a FLAMMABLE (Class 3) placard and Guide 153 for a CORROSIVE (Class 8) placard. Guide 111 is the fallback when a DANGER or DANGEROUS placard is displayed, when the material is unknown, or when hazardous materials are suspected but no placards can be seen. The how-to flowchart also routes explosives placards: Guide 112 for Divisions 1.1, 1.2, 1.3 or 1.5 and Guide 114 for Divisions 1.4 or 1.6.

If multiple placards point to more than one guide, the ERG says to start with the most conservative guide, meaning the one that calls for the greatest protective action. Once the ID number or proper shipping name is known, you must switch to the more specific guide for that material.

All guide numbers in the 2024 edition

Titles are as printed in the orange section. Guides 111 to 128 cover the load types people meet most often: mixed loads, explosives, gases and flammable liquids.

Guides 111 to 139: mixed loads, explosives, gases, flammable liquids and solids, reactive substances

Guides 140 to 174: oxidizers, organic peroxides, toxic substances, radioactive materials and others

Worked example

A tank trailer carries a red placard with the flame symbol and the number 3, and the driver is unconscious so there is no shipping paper to read. Match the FLAMMABLE placard in the placard table and you land on Guide 127. Open the orange section to Guide 127, titled Flammable Liquids (Water-Miscible), for the potential hazards, public safety, emergency response and first aid pages. The moment an ID number such as 1203 or a name such as gasoline is read from the panel, look it up in the yellow or blue pages: it points to its own guide, which may be Guide 128 for water-immiscible flammable liquids, and that guide replaces the placard guide.

What this page does not do

It does not list the ID number index. The yellow and blue pages are long two-column indexes, so use the guidebook itself or an official ERG app for a number-to-guide lookup. TNAADO already has a UN number lookup built on 49 CFR 172.101, but that table gives class, packing group and labels, not the ERG guide. We read the PHMSA PDF of the ERG 2024 through the Internet Archive copy captured on October 31, 2026 because the PHMSA server refused our automated request. In an emergency call 911 and the emergency response telephone number on the shipping paper first.

Sources

Sources opened and read November 2, 2026.

• PHMSA: Emergency Response Guidebook (ERG) page (read November 2, 2026)
• PHMSA: ERG 2024 English PDF (read via the Internet Archive capture of October 31, 2026) (read November 2, 2026)