H-class HEPA filtration removes 99.99% of particles at 0.3 microns — the particle size that is hardest to capture and, not coincidentally, small enough to reach deep into the lungs and stay there.
What matters as much as the grade is where the element sits. Put filtration only on the inlet and you protect the machine: the fines are stopped before they reach the power section, and the cartridge blinds steadily until airflow collapses. Put an H-class element on the exhaust and you protect the room, because the air leaving the machine has been through it.
Why exhaust-side filtration is the right way round
An industrial vacuum moves a great deal of air, and all of it eventually leaves the machine. On a unit without exhaust filtration, everything that gets past the inlet cartridge — and on fine dust a surprising amount does — is discharged back into the workspace at velocity. The floor looks clean and the breathing zone is worse than it was.
The arrangement used here is a coarse or anti-static cartridge at the inlet to handle bulk, a cyclone ahead of it on the dust units, and the H-class element on the exhaust as the final barrier. Each stage does the job it is suited to, and the inlet filter is not being asked to be a respirator.
The materials that make it necessary
- Respirable crystalline silica — concrete cutting and grinding, engineered stone, tunnelling. The reason H-class is written into so many method statements.
- Lead — paint removal, battery work, firing ranges, older industrial demolition.
- Asbestos — removal and remediation work, where H-class is the required grade.
- Metal fines — aluminium, magnesium and zinc, which are both a health exposure and an explosion risk.
- Pharmaceutical actives — potent compounds in small quantities.
- Hardwood and composite dust — a recognised carcinogen in its own right.
Representative units
| Filter grade | H-class, 99.99% efficiency at 0.3 microns |
|---|---|
| Position | Exhaust-side terminal box, downstream of the power head |
| 60 litre stainless, explosion proof | 100 CFM air supply, around 130 CFM flow, 16–17" Hg, tipping tank |
| 90 litre poly tank | From 75 CFM, wet and dry, HEPA on exhaust |
| Cyclone trolley unit | 100 CFM, 60 litre stainless capture tank, aluminium frame, tipping bin |
| Reverse filter clean drum top | 150 CFM supply, around 200 CFM flow, cyclone and HEPA terminal |
| Hose | 38 mm and 50 mm; practical run shortens on wet duty |
| Lead time | HEPA elements are made to order — allow additional build time |
Ergonomics on the emptying end
There is no point capturing a hazardous dust perfectly and then releasing it while emptying the machine. The cyclone units use a bin on a tipping frame, cantilevered so the operator rotates it rather than lifting it — which removes both the manual handling risk and the cloud that comes off a bin being hoisted and tipped by hand.
Spillrite has supplied pneumatic explosion-proof vacuums fitted with HEPA filtration to the Australian Defence Department and to Airbus Group Australasia. The HEPA-fitted pneumatic explosion proof vacuum carries NATO stock number 7910-66-158-5157.
If the dust is also an explosion risk — which for metal fines and most organic powders it is — read combustible dusts alongside this, because the cyclone and the certification matter as much as the filter grade.