Dust Hazard Analysis (DHA) for Metal Dust: Aluminum, Magnesium, Titanium, and More

By DHA Report Group · Updated October 20, 2026

If your facility grinds, polishes, sands, cuts, blasts, or 3D prints metal, your dust needs a closer look than most. Metal dusts can burn hotter than organic dusts, some react with water, and the standard that used to cover them, NFPA 484, is now part of NFPA 660. Your dust hazard analysis (DHA) has to account for all of that.

Which metal dusts are the concern?

The most reactive, and the ones that get the most attention, are:

• Aluminum
• Magnesium
• Titanium
• Zirconium
• Niobium and tantalum

Other metals, like iron and zinc, can also form combustible dust when fine enough. Not all metal dust is combustible, and typical steel grinding dust generally is not, so testing settles the question. Welding, laser cutting, and plasma cutting fume should be treated as in scope until testing shows otherwise.

Why metal dust is handled differently

• Hotter, faster fires. Some metal dusts burn at very high temperatures and are hard to put out once burning.
• Water can make things worse. Burning combustible metals can react with water. Water is the wrong agent for almost all of them, iron and steel being the main exception, and a Class D agent is often needed.
• Hydrogen. Reactive metal fines in water, including in wet collectors, can generate hydrogen gas. That has to be managed with ventilation and design.
• Mixed dusts. Aluminum mixed with other dusts, or metal dust near solvents, can change the hazard.

Collection: wet vs. dry

For most reactive metals, NFPA 660 prefers wet collectors, with dry collection located outdoors as the recognized alternative. Indoor dry collection of combustible metal dust is treated as a last resort, used only when wet or outdoor dry collection is not feasible, and then with added protection. For some metals, like niobium and tantalum, dry collection is not recommended at all. Whatever you run, a wet collector handling combustible metal needs hydrogen management built in: venting the hydrogen to a safe place, and water-level monitoring that shuts the collector and the process down on low or high water.

Your DHA looks at what you collect, what collector type you have, where it sits, and whether it fits your metal. Where a collector serves metal dust, isolation between the collector and your building has to be evaluated. The standard’s exemption that lets some systems skip isolation does not apply to metal dust.

Where a DHA looks in a metal facility

• Grinding, polishing, deburring, and sanding stations
• Machining with dry chips and fines
• Blasting booths
• Additive manufacturing powder handling, sieving, and cleanup
• Collectors, ductwork, and how collected material is removed and stored
• Housekeeping and the vacuums used to clean up metal dust
• Fire response: what agent is on hand and whether your team knows not to use water

Common gaps in metal facilities

• Dry collectors indoors serving aluminum or magnesium grinding
• Wet collectors without hydrogen venting or ventilation
• Mixing metal dust with other dusts in one collector
• Standard shop vacuums used on metal fines
• No Class D extinguishing agent near metal work
• Sludge from wet collectors left to dry out

Getting started

Have your layout, the metals and alloys you process, your collector details, and any test data ready. Published values for metal dusts are for screening only. Any protection design needs testing of your own dust, because particle size, moisture, and alloy change the results. See what a DHA costs in 2026 and who counts as a qualified person.

Keep reading

• NFPA 484 Is Now NFPA 660: What It Means for Combustible Metal Facilities
• Dust Collector Explosion Protection: Venting, Isolation, and Suppression Explained
• Combustible Dust Testing Explained: KSt, Pmax, MEC, and MIE
• Is My Dust Combustible? How to Find Out Before Your DHA

Questions about metal dust

Is aluminum dust combustible?

Yes. Fine aluminum dust is a combustible metal dust and one of the more reactive ones.

Do I need a wet collector for aluminum dust?

NFPA 660 prefers wet collection for most reactive metals, with outdoor dry collection as the recognized alternative. Your DHA will look at your specific setup.

Can I use water on a metal dust fire?

Usually not. Water is the wrong agent for almost all burning combustible metals, iron and steel being the main exception. A Class D extinguishing agent is usually the right tool.

Is welding fume a combustible dust?

Treat it as in scope until testing shows otherwise. A DHA will look at how it is collected.