WOW!!!One REALLY dirty air filter!!!!I vacuum the outer filters on my 'Lux units every week.Yes,gives an excuse to use the vacuum.The air purifier machines--the HVAC filters now last for MONTHS!!!By the way hows yours??I have also seen similar filter elements in Cat genset engine filters that bad-but the engine still worked!The filter element is ahead of the engine turbocharger.Amazing how much suction an exhaust powered turbocharger can generate!After all it is like a GIANT Kirby fan!The 3816 series Cat engine our genset at work has two large turbochargers with giant pleated air filters.Yes,like those in purifiers-just bigger.