Classification reference
Class I, Division 1: flammable gas and vapour
Class I covers flammable gases, flammable liquid-produced vapours and combustible liquid-produced vapours. Division 1 is the more severe of the two divisions: the hazardous atmosphere is expected to be present during normal operation, not just when something fails.
- Class I = flammable gases and vapours (not dust — dust is Class II)
- Division 1 = ignitible concentration expected under normal operating conditions
- Groups A, B, C and D rank gases by ignition severity
- Equipment must be suitable for the Class, Division, Group and temperature code together
What the classification actually says
Under the North American scheme, a Class I location is one where flammable gases or vapours may be present in the air in quantities sufficient to produce an ignitible mixture. Division 1 applies where that mixture can exist under normal operating conditions, where it may exist frequently because of repair or maintenance work or leakage, or where equipment failure could simultaneously release the hazard and create an ignition source.
The practical difference between Division 1 and Division 2 is expectation, not possibility. Division 2 locations are those where the flammable material is confined in normal operation and only escapes if containment fails. If an operator would expect to smell solvent during a routine shift, that is a Division 1 conversation.
Groups A, B, C and D
Class I locations are further divided by the gas or vapour present, because ignition energy and flame-transmission behaviour differ sharply between them. Group A covers acetylene, Group B hydrogen and gases of comparable hazard, Group C ethylene and similar, and Group D the large family that includes propane, methane, most common hydrocarbons and many industrial solvents.
Group D is the group most frequently encountered in general manufacturing, and it is among the Class I groups PrestiVac's explosion proof vacuums are certified for. Equipment certified for a less severe group is not acceptable in a more severe one — a Group D listing does not carry into a Group B hydrogen area.
Temperature codes
Classification is not complete without a temperature code. The code caps the maximum surface temperature the equipment may reach, and it must stay below the ignition temperature of the material in the surrounding atmosphere. The principal codes run T1 (450 °C) through T6 (85 °C), with the North American scheme subdividing several of them — T3C, which appears on the EX1 certificate, sits within the T3 band.
Confirm the specific temperature-code figures against the current code edition and the equipment certificate before relying on them for a design decision. The number on the certificate governs, not a general table.
Where dust and gas overlap
Plenty of real facilities are not purely one or the other. An ethanol plant handles grain dust and flammable vapour; a coatings plant handles powder and solvent. Where both are present, each is assessed on its own terms and the equipment has to satisfy whichever requirement is more demanding in that space.
Classification is assigned by your own electrical or process engineer and accepted by the authority having jurisdiction. Bring that classification to the equipment conversation rather than working backwards from a product.
What this means when you specify recovery equipment
In a Class I, Division 1 area every piece of equipment brought into the space — including cleaning equipment — has to be suitable for the classification. That is why a shop vacuum is not a marginal choice but a prohibited one: its motor brushes spark by design.
Two approaches are common for recovery equipment. The first is certified explosion-protected electrical construction appropriate to the Class, Division and Group. The second removes the electrical question entirely: an air-operated vacuum driven by compressed air has no motor, no switch and no cord in the unit at all.
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.
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 is Class I, Division 1?
- A location where flammable gases or vapours are present in the air in ignitible concentrations under normal operating conditions — or may be present frequently through maintenance, repair or leakage. It is the more severe of the two Class I divisions, and equipment used there must be suitable for the specific Class, Division, gas Group and temperature code.
- Is Class I about dust?
- No. Class I is gases and vapours. Combustible dust is Class II, and ignitible fibres and flyings are Class III. Facilities often have both, but they are classified and assessed separately.
- Can one vacuum cover Class I and Class II areas?
- Only if its certification covers both, and the specific Groups involved. PrestiVac's EX1 HEPA line, for example, is certified for Class I, Group D and Class II, Groups E, F and G under UL 1203 certification. Certification documentation is available for the configuration you are specifying.
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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