Hazard communication
Category 1 vs NFPA "4": the numbering trap that confuses workers
In the GHS, 1 means most dangerous. In the NFPA diamond, 4 means most dangerous. Mixing them up can lead to wrong decisions in an emergency.
Many imported chemicals arrive with two hazard systems on the same packaging:
- the GHS label, required in Uganda by the Hazardous Chemicals Regulations, 2024;
- the NFPA 704 "fire diamond", a US system widely used for emergency response.
Both use numbers to rank how severe a hazard is, but in opposite directions.
| GHS hazard category | NFPA 704 rating | |
|---|---|---|
| Most severe | Category 1 (sometimes split into 1A and 1B) | 4 |
| Least severe | Category 4 or 5, depending on the class | 0 |
| Purpose | Classification and hazard communication for supply and use | Quick reading for firefighters and emergency responders |
| Legal status in Uganda | Mandatory | Supplementary only |
How to read the NFPA diamond. It has four coloured quarters:
- blue: health hazard, 0–4;
- red: flammability, 0–4;
- yellow: instability or reactivity, 0–4;
- white: special hazards, such as OX (oxidiser) or W with a line through it (reacts with water; do not use water).
Where it goes wrong. A worker who knows only the NFPA system may see "Category 1" on a GHS label and assume it means low risk. In fact it is the most severe category. The reverse also happens: a "4" in the blue quarter can be taken as mild. On a corrosive or highly toxic chemical, that misreading can lead to the wrong PPE or a delayed evacuation.
The rule to teach. Always use the GHS label and the SDS for decisions about handling, storage and PPE. Treat the NFPA diamond as a quick visual cue, especially for fire response, never as a replacement.
What to do
- Cover both systems in induction training, and say plainly that the numbers run in opposite directions.
- Put a side-by-side poster at stores and decanting points.
- In toolbox talks, show a real drum that carries both markings and ask workers to read each one.
- In risk assessments, record the GHS category, not the NFPA number.
How INRC can help
Our training covers both systems side by side, with real drums and practical exercises, so workers read hazard ratings correctly in an emergency. See also our occupational health and safety services. Contact us to discuss your site.
This article is general guidance, not legal advice. Check current legislation and regulations for your specific project.