Plenum cleaning: the space above the filters

It's the chamber inside the canopy, behind (or above) the grease filters, where the filtered air collects before entering the ductwork - a real part of the system, but hidden behind the filters. The plenum is the air chamber within the canopy, sitting behind the grease filters: as the cooking vapour passes through the filters, the air collects in the plenum before it enters the ductwork. So it sits between the filters and the duct, inside the canopy. It's a defined component of the extraction (gathering and channelling the filtered air into the duct), but it's out of sight behind the filters. Because some grease always gets past the filters, the plenum accumulates grease - and because it's hidden behind the filters, it's easily missed in a clean. So the plenum is the hidden chamber behind the filters that collects grease and needs cleaning as part of the whole system. So it's the chamber behind the filters where the air collects. This is general commentary on the plenum.

Because some grease always gets past the filters, and the plenum is the first space the air passes through after them - so grease that gets through settles in the plenum. The grease filters catch a lot of the grease, but not all - some always gets past even good filters (and more past clogged or poor ones). The plenum is where the air collects immediately after passing through the filters, so the grease that got past them starts to deposit there - on the plenum's surfaces, walls and features - as the air slows and collects before entering the duct. So over time the plenum accumulates grease, like the canopy and ductwork. And the worse the filters, the more grease reaches the plenum. So grease builds up in the plenum because the filters don't catch everything, and the plenum is where the escaping grease first settles. This makes it a grease-collecting space that needs cleaning. So grease builds up because some gets past the filters into it. So because grease gets past the filters. This is general commentary.

It should be, as part of a proper whole-system clean - but because it's behind the filters, it's easily missed by a superficial clean; a thorough clean reaches behind the filters to clean it. A proper extraction clean covers the whole system, and the plenum (behind the filters) is one of the parts - a thorough clean removes the filters and cleans the plenum chamber, along with the canopy, filters, ductwork and fan. So it should be cleaned. But because the plenum is out of sight behind the filters, it's easily overlooked - a superficial or hurried clean can do the visible canopy and filters but skip the plenum behind them. So whether it's cleaned depends on the thoroughness of the clean: a proper whole-system clean includes it, a poor one may miss it. This is why the plenum is one of the places to check was cleaned (looking behind the filters). So it should be cleaned in a proper clean, but is easily missed by a poor one. So it should be, but poor cleans miss it. This is general commentary.

Look behind the filters into the plenum chamber - if it's clean, it was done; if it's still greasy, it was missed; this is one of the checks when auditing a clean. Because the plenum is behind the filters, checking it means removing or looking behind a filter and inspecting the plenum chamber: if the surfaces are clean, the plenum was cleaned; if they're still coated in grease, it was skipped. This is one of the useful checks when auditing an extraction clean (along with checking the ductwork at an access panel and the fan) - the plenum being one of the hidden spaces a less-thorough clean might miss. So to check, look behind the filters into the plenum and see whether it's clean or greasy. A proper clean will have cleaned it; if it's greasy, raise it with the cleaner (as part of ensuring the whole system was done). So check by looking behind the filters at the plenum chamber. So look behind the filters for grease. This is general commentary.

Yes - grease building up in the plenum is a fire risk like any grease build-up in the system; it's combustible fuel in the extraction, so it should be cleaned as part of controlling the fire risk. The plenum accumulates grease (that gets past the filters), and that grease is combustible - so a grease-laden plenum is a fire risk, like grease anywhere in the extraction system. It's part of the system's total grease load that fuels the fire risk. So a neglected plenum (grease building up in it, hidden behind the filters) contributes to the fire risk and should be cleaned to control it. This is why the plenum can't be ignored just because it's out of sight - the grease in it matters for fire safety like the grease in the canopy, ductwork and fan. So cleaning the plenum (as part of the whole-system clean) is part of removing the grease and controlling the fire risk. So yes - a grease-laden plenum is a fire risk to clean. So yes - it's grease fuel in the system. This is general commentary.

The canopy is the whole hood over the cooking (the visible part); the plenum is the chamber inside it, behind the filters, where the filtered air collects - so the plenum is a specific space within the canopy. The canopy is the hood mounted over the cooking line - the visible structure that collects the rising vapour, holds the grease filters, and connects to the ductwork. The plenum is a specific part inside the canopy: the chamber behind (or above) the grease filters, where the air collects after passing through the filters and before entering the ductwork. So the plenum is a space within the canopy, not the same as the whole canopy - it's the chamber behind the filters specifically. Both need cleaning (they both collect grease), but the plenum is the more hidden, easily-missed part (behind the filters), while the canopy includes the visible parts too. Knowing the distinction helps ensure the plenum (the hidden chamber) isn't overlooked when the canopy is cleaned. So the canopy is the whole hood; the plenum is the chamber behind the filters within it. So the plenum is a chamber inside the canopy. This is general commentary.