Glossary
Quick answer
Pascals measure sealed suction pressure with the inlet blocked. Air watts measure useful work at the cleaning head, combining airflow and pressure. There is no valid conversion between the two, so compare pascals against pascals and air watts against air watts, within one machine type.
Unit definitions and published specifications.
Suction units
| Unit | Measures | Limitation |
|---|---|---|
| Pascals (Pa) | Sealed suction pressure, with the inlet blocked. | It says nothing about airflow, and airflow is what carries dust into the bin. A machine can post a huge sealed figure and still pick up poorly through a narrow or leaky path. |
| Kilopascals (kPa) | The same sealed pressure, in units of one thousand pascals. | Watch for it in marketing: a smaller looking number in kPa is not a weaker machine. |
| Air watts (AW) | Useful work at the cleaning head, combining airflow and pressure. | It is measured at the manufacturer's chosen point and mode, usually boost, and boost is not the mode you clean a whole house in. |
| Cubic feet per minute (CFM) | Volume of air moved per minute. | Rarely published for household machines, and useless without knowing where it was measured. |
| Water lift (inches) | Sealed pressure expressed as the height of a column of water it can raise. | Same limitation as pascals: it is a blocked-inlet figure, not a cleaning figure. |
There is no valid conversion between pascals and air watts. Pascals describe pressure with the inlet sealed; air watts describe work done while air is actually moving. A chart that converts one into the other is inventing a relationship that does not exist, so compare pascals against pascals and air watts against air watts, and only within the same machine type.
Machine types
| Type | What it is | Expected life |
|---|---|---|
| Robot vacuum | A self navigating disc that cleans on a schedule. It trades outright pickup for the fact that it actually runs. | 3 to 6 years |
| Cordless stick | A battery powered wand. The most used machine in most homes because it is the easiest one to pick up. | 4 to 7 years |
| Upright | A motorised brush roll driven across carpet by a full size motor on mains power. | 6 to 10 years |
| Canister | A separate body on wheels with a hose and interchangeable heads. The long life choice. | 8 to 15 years |
| Wet dry floor washer | A machine that lays down clean water, scrubs, and lifts the dirty water back into a second tank. | 3 to 6 years |
| Carpet cleaner | A deep cleaner that injects detergent solution into carpet and extracts it again. | 5 to 10 years |
| Handheld | A small battery unit for spot jobs, car interiors and worktops. | 3 to 6 years |
Filter types
| Filter | Washable | Note |
|---|---|---|
| Foam pre-filter | Yes | Rinse monthly, dry fully for 24 hours before refitting. |
| Felt or cloth filter | Yes | Tap out monthly, rinse quarterly, dry fully. |
| Pleated cartridge | No | Tap out the dust; do not wash unless the maker says washable. |
| Sealed HEPA cartridge | No | Replace on schedule. A HEPA element that is washed is no longer a HEPA element. |
| Exhaust or charcoal filter | No | The one people forget. It is why a clean machine still smells. |
Robot navigation
| System | How it works | Limitation |
|---|---|---|
| Lidar (a spinning laser turret) | A laser rangefinder sweeps the room and builds a dimensioned map. | The turret adds height, so the robot may not fit under low furniture. |
| vSLAM (a camera looking up) | A camera picks landmarks on the ceiling and walls and works out position from how they move. | Needs light. In a dark room it falls back to a less accurate mode. |
| Gyroscope and bump | Dead reckoning from wheel rotation and an inertial sensor, correcting when it hits something. | No persistent map, so no zones, no room selection, and missed patches in complex layouts. |
| Obstacle avoidance (structured light or a second camera) | A forward sensor identifies objects in the path and steers around them. | Recognition is not perfect, and a camera based system is a camera in your home. |
Everything else
| Term | Definition |
|---|---|
| Agitation | The mechanical action of a brush roll flicking carpet pile open so airflow can carry dirt out of it. On carpet this accounts for more of the result than suction does. |
| Sealed filtration | A machine where all the air that passes the motor also passes the filter, with no leak path around it. Fitting a HEPA element to an unsealed machine does not make it a sealed system. |
| Sealed suction | Pressure measured with the inlet completely blocked. It is the largest figure a machine can quote and it describes a condition you never clean in. |
| Self cleaning brush roll | A roll with a comb or blade that cuts wrapped hair as it turns. The feature that matters most in a home with shedding pets or long hair. |
| Soft roller | A fabric covered roller built for hard floors. It captures fine dust and large debris without the stiff bristles that can mark a sealed finish. |
| Thermal cutout | A protective switch that stops a motor when it overheats or stalls, and resets on its own once it cools. It is why a machine must be unplugged before a hand goes near a brush housing. |
| Water lift | Sealed pressure expressed as the height of a column of water the machine can raise. One inch of water lift is about 249 pascals. |
| Dead reckoning | Navigation by counting wheel rotations and sensing turns, with no map. Cheap, and adequate in a small flat with simple rooms. |
| No-go zone | An area drawn on a robot vacuum map that the machine will not enter. It requires a system that keeps a persistent map, which rules out gyroscope-only navigation. |
| Bin restriction | The loss of airflow that happens as a bin or bag fills. It begins well before the container looks full, which is why emptying on a schedule beats emptying on appearance. |
Common questions
What is the difference between pascals and air watts?
Pascals measure sealed suction pressure, taken with the inlet completely blocked, which is the largest figure a machine can quote. Air watts measure useful work at the cleaning head by combining airflow with pressure, so the figure tracks what a machine can actually lift. They describe different quantities under different conditions and cannot be converted.
What does sealed filtration actually mean?
That every bit of air passing through the machine also passes through the filter, with no leak path around the element. This matters more than the filter grade: an unsealed machine with a HEPA element fitted leaks fine particles around the edge of the filter and the rating becomes largely meaningless in practice.
Is a higher pascal figure always better?
Within one machine type and usually within one manufacturer, it correlates with something real. Across brands and especially across machine types it correlates with marketing, because no maker is required to publish a standard test. Head design, agitation and filtration decide more of the outcome than the headline number does.
What is agitation and why does it matter so much?
It is the mechanical action of a brush roll flicking carpet pile open so that airflow can carry the dirt out. Carpet holds dirt down in the pile where suction alone cannot reach it, which is why a machine with an enormous sealed figure and a worn brush roll still leaves a carpet looking dull.
What is the difference between lidar and vSLAM?
Lidar sweeps a laser rangefinder and builds a dimensioned map, so it works in the dark and produces tidy parallel rows, at the cost of a turret that raises the machine. vSLAM watches landmarks with an upward camera, which sits lower and costs less but needs light and degrades in a dark room.
Every figure here comes from published manufacturer specifications, owner reported measurements and repair documentation, and each is labelled as either a standard or a convention. This is researched general information to help you diagnose and plan, not professional advice, and it cannot tell you what is wrong with one particular machine. Your own manual and the part number printed on your machine are the final word.