All I've ever done is hoover them, sucking on the outside. Doesn't work very well.
What I havn't tried is to hoover them in the filter housing, with the air intake taped to the hoover, sort of pneumatic back-flushing, though it'd be good if the reverse flow air into the filter was fairly clean.
Some bad oil analysis results, claimed to be due to air filter cleaning (I assume with compressed air)
This is an interpretation of the results and, while it seems reasonable, doesn't seem to have been definitively proved.
It also seems to assume that filter-cleaning is inherently wrong. In other words, it makes no distinction between cleaning them "well" and cleaning them "badly".
These may be cases where dirt has been blown into the engine or the filter has been damaged. The consequences of this are likely to be worse in South America (or here in Southern Taiwan) than in the UK.
would disagree with you. They SELL a pneumatic back-flushing gadget, (As I suggested above. Like most of my nominally clever/fairly obvious ideas, it's already being done.)
This is aimed at construction/farming/mining plant which of course will clog filters a lot quicker/more expensively than most private cars.
The testing they detail isn't very scientific, pretty close to anecdotal evidence in fact, though that doesn't mean its wrong.
In particular, "damage" is operationally defined as "light doesn't shine through it". That'd be a good way of spotting actual holes, but I might want tighter criteria before I risked my shiny new bulldozer on it.