Classification reference
Class II Groups E, F and G: how dusts are grouped
Class II locations are subdivided by the dust itself, because conductivity and combustion behaviour differ enormously between aluminium powder, coal dust and flour. Equipment is certified to specific Groups — which is why a general claim of dust suitability tells you very little.
- Group E: combustible metal dusts — conductive and treated most severely
- Group F: carbonaceous dusts including coal, coke and carbon black
- Group G: non-conductive combustible dusts — flour, grain, wood, plastics, chemicals
- Certificates name the Groups explicitly; read them rather than inferring
Group E — combustible metal dust
Group E covers combustible metal dusts including aluminium, magnesium and their commercial alloys, together with other dusts whose particle size, abrasiveness and electrical conductivity present comparable hazards. Two properties make this group the most demanding: the dusts burn ferociously once ignited, and because they conduct they can bridge terminals and short electrical equipment.
Reactive metal fines bring further complications that classification alone does not capture — several react with water to liberate hydrogen, which rules out the instinctive response to a fire and shapes how recovered material is stored and disposed of.
Group F — carbonaceous dust
Group F covers carbonaceous dusts: carbon black, charcoal, coal and coke. The characteristic behaviour here is smouldering. A deep-seated glow can persist inside accumulated material long after the visible event, then reignite — which is why recovered coke and coal dust is not left sitting in a collection container at the end of a shift.
Group G — non-conductive combustible dust
Group G is the broadest group: combustible dusts that are not electrically conductive. Flour, starch, grain, sugar, wood, paper, many plastics, pharmaceutical powders and a wide range of chemical dusts sit here. Most food and wood processing plants are Group G facilities.
Non-conductive does not mean lower consequence. The flour and grain explosion record is the reason dust hazards became a regulated engineering subject in the first place.
Reading a certificate properly
A certificate that names Class II, Groups E, F and G covers all three families; one that names only Group G does not extend to metal dust. Along with the Groups, check the Class, the Division, the temperature code and the described scope of the equipment — the scope line is what ties the marking to a specific product family.
PrestiVac's listing is CSA Certificate 70122393 (Master Contract 268761), assessed against UL 1203 (5th Edition) among other standards. It carries two distinct scopes: the EX1 HEPA drum-type line is covered for Class I, Gp. D; Class II, Gps. E, F and G; Temp. Code T3C; the EV EX HEPA line is covered for Cl. II, Div. 2, Gps. F and G. The EV scope is narrower — no Class I, Division 2 only, and Groups F and G only, which excludes Group E conductive metal dusts. Commercial, indoor use only, in hazardous locations.
What this means when you specify recovery equipment
Match the certificate to the dust you actually have, not to the dust the plant is named after. Mixed facilities are common: a metalworking shop with a wood shop attached spans Groups E and G, and the equipment used across both has to cover both.
Group E work in particular tends to drive additional configuration decisions — immersion separation for reactive fines, conductive accessories throughout, and disposal practices that keep recovered material from accumulating dry.
Area classification is determined by your own engineering assessment and the authority having jurisdiction. This page explains the framework; it is not a classification of your facility, and it does not replace the applicable code or your Dust Hazard Analysis.
Frequently asked questions
- What are Class II Group F and Group G dusts?
- Group F is carbonaceous dust — coal, coke, charcoal and carbon black, characterised by a tendency to smoulder. Group G is the non-conductive combustible dusts: flour, grain, sugar, wood, paper, plastics, pharmaceutical and many chemical powders. Group E, by contrast, is conductive combustible metal dust.
- What is a Class II vacuum cleaner?
- Informally, a vacuum suitable for use in a Class II combustible-dust location. What makes it suitable is its certification for the specific Class, Division, dust Group and temperature code of your area — plus the practical construction that goes with it: conductive, grounded and bonded throughout, anti-static accessories, and filtration that keeps fines out of the drive and the exhaust.
- Does a Group G listing cover aluminium dust?
- No. Aluminium is a Group E conductive metal dust. Equipment certified only for Group G does not extend to Group E, and metal dust also raises reactivity questions that Group G materials do not. Confirm the Groups named on the certificate against the dust present in your process.
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