Buying guide
8 min read
Selecting a vacuum for metal dust
Metal dust is the application where the certification detail stops being paperwork and starts deciding what you can buy. Group E is the conductive metal-dust group, and it is not inside every listing — so the first question is not which vacuum, but which of them are certified for the group your material sits in.
- Group E is conductive metal dust and it narrows the eligible equipment
- Some metals react with water — wetting cannot be assumed safe
- Freshly generated fines can be pyrophoric
- Mixing metals in one container is its own hazard
Start with the group, not the machine
Class II dusts are divided into groups, and metal dust sits in Group E because it is electrically conductive. That conductivity is a hazard in its own right: accumulated metal dust can bridge and short electrical equipment, causing failures that create the ignition source everything else is designed to exclude.
This matters commercially because Group E is not inside every certified scope. PrestiVac's CSA listing carries two scopes, and only one of them includes Group E — the EX1 HEPA line. The EV EX HEPA line is covered for Groups F and G only. Two units that look similar and sit in the same catalogue are not interchangeable for this application, which is why each model page states its own scope.
Water reactivity changes the method
Several metals react with water to produce hydrogen, which introduces a flammable gas into an event that was already a fire. That rules out assumptions in two directions: water is not a universal extinguishing answer, and wet or immersion recovery cannot be assumed appropriate.
Immersion separation — drawing material into a liquid bath so it is wetted on capture and never forms a dry cloud inside the machine — is a genuinely effective control for some metal dusts and inappropriate for others. Which applies is a property of the specific alloy as your process generates it, established by testing rather than by the metal's general reputation.
Pyrophoric behaviour in fresh fines
Grinding, machining, polishing and blasting produce fine, freshly exposed, chemically active particles. Some can ignite spontaneously on exposure to air. The stock is stable; the swarf may not be.
The practical consequence is that accumulation time matters. Material left in a machine sump or a collection container is not in the same condition it was when generated, and the interval between recovery and disposal belongs in the specification rather than being left to whoever empties it.
Do not mix metals
Different metals collected into a common container can react with each other. Dedicated recovery per material is the normal arrangement in metalworking and additive manufacturing, and it is a safety decision rather than a housekeeping preference.
In additive manufacturing there is a commercial reason pointing the same way: powder is expensive, operations reclaim and re-sieve it, and a recovery method that contaminates or mixes alloys destroys the feedstock value as well as creating a hazard.
What the specification has to cover
Beyond the group and the water question: a conductive, grounded and bonded path from tool to container, because dry metal dust moving through a hose generates charge readily. Smooth internal construction without ledges where material can accumulate. A container that can be removed and sealed without a second dispersal event.
Filtration matters for a reason particular to metals — many are toxic as well as combustible. Retained absolute filtration is an exposure control here, not only a housekeeping one.
What differs from an organic dust application
| Aspect | Organic dust (Group G) | Metal dust (Group E) |
|---|---|---|
| Certified scope | Within both PrestiVac scopes | EX1 HEPA line only |
| Conductivity | Non-conductive | Conductive — can bridge electrical equipment |
| Water | Generally usable | May react — must be established by testing |
| Fresh fines | Stable | May be pyrophoric |
| Shared container | Often acceptable | Different metals can react — dedicate per material |
| Filtration driver | Housekeeping and hazard | Also toxicity and exposure |
Confirm the line against your classification
Group E coverage is the deciding factor and it differs between our two certified scopes. Bring the material and the area classification assigned by your engineer, and we will confirm which line applies.
Where the material has not been characterised, testing it as your process generates it comes before the equipment decision.
Frequently asked questions
- Which PrestiVac line is certified for metal dust?
- The EX1 HEPA line. Its scope on CSA Certificate 70122393 includes Class II Groups E, F and G, and Group E is the conductive metal-dust group. The EV EX HEPA line is covered for Groups F and G only, so it does not carry Group E coverage.
- Can we vacuum aluminium and titanium into the same unit?
- Not into a shared container. Different metals collected together can react with each other, so dedicated recovery per material is the normal arrangement. In additive manufacturing it is also what protects the reclaim value of the powder.
- Is immersion separation right for metal dust?
- For some materials, and not for others. It wets material on capture so it never forms a dry cloud inside the machine, which is effective — but several metals react with water. Whether it applies to your material is established by testing rather than assumed.
- Does the vacuum need to be conductive throughout?
- The recovery path does. Dry metal dust moving through a hose generates charge readily, so the requirement is a continuous conductive path from tool through hose to container, bonded and grounded — not simply a grounded machine.
Talk to the manufacturer
Get the right explosion proof vacuum for your application.
Tell us what you need to vacuum and where. Our technical team will recommend the PrestiVac model best suited to your material, your classification and how hard you will work it — and because we build every unit ourselves, we can modify it to fit.
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