Air Purifiers

The filter stack inside an air purifier:

almost every machine worth having uses the same three layers. A washable mesh prefilter catches hair and lint, a pleated HEPA sheet catches the fine dust, and a layer of activated carbon takes up smells. Look for “true HEPA” or an H13 grade on the box; “HEPA-type” is a marketing phrase for a looser filter. An ionizer or UV-C lamp is an extra on top, not a substitute for the sheet. Not everything listed as a purifier is one. An ozone generator is built to deodorise an empty room, not to run beside you while you sleep, and an ionizer with no filter mostly moves dust out of the air and onto the walls. A recirculating cooker hood sold to clear kitchen smells is not one either, and belongs with extractor hoods. A wardrobe that smells of damp needs one of the dehumidifiers, and a tower fan with an “ion” button is still one of the fans.

Traffic soot on the main avenues and the room size on the box:

the capital’s dirtiest air comes from traffic, and it peaks at rush hour around El Trébol and the big arterial roads. A flat facing one of those roads turns a prefilter grey far faster than one on a quiet residential street, and the carbon layer earns its place there because diesel exhaust carries a smell as well as soot. Size the machine to the room, not the house: the box gives a room size or a clean-air delivery rate (CADR), and a compact tower meant for a bedroom will not keep up in an open-plan living room. In a bedroom the noise on the lowest setting matters more than the top speed, so check that the sleep mode really dims the display.

Cartridges decide what an air purifier is worth:

a compact HEPA purifier for a bedroom, from Xiaomi, Levoit or Honeywell, costs around Q700 to Q1,000 new, and a Dyson purifier-fan reaches roughly Q5,000. The machine itself is a fan, a motor and a sensor and seldom fails; what wears out is the cartridge, and each brand shapes its own. Filters for the common brands are easy to replace, but for the less common ones the cartridge often has to be ordered from abroad. Price a used purifier as a new one minus a fresh cartridge, and lower still when nobody nearby stocks the filter it takes.

Grey prefilters, reset lights and filters that do not seal:

open the back before anything else. A grey prefilter is normal and washes clean; a HEPA sheet that has gone dark, or smells of smoke or kitchen grease, needs replacing whatever the seller says. On most machines the filter-change light counts running hours rather than measuring anything, so a freshly reset light proves nothing about the sheet. Check that the cartridge sits snug in its frame, because a cheap compatible filter that leaves a gap lets air slip round it. Run it on high and listen for a motor rattle. On models with an air-quality light, shake a dusty cloth near the intake and watch the colour change; if it never moves, the sensor has failed and auto mode is useless.

Listing a purifier with its model number and filter date:

the model number tells a buyer which cartridge fits and whether they can get one, so put it in the title. Photograph the base label, the filter out of the machine and the display running. Say when the filter was last changed, and include a spare if you have one, since a sealed cartridge in the box can be what closes the deal. If the purifier connects to the brand’s app, unlink it from your account before handing it over, or the new owner cannot set it up. A compact tower fits in a shopping bag for the bus back to Escuintla, and whoever collects it will want to see it switch on and the colour ring react before they pay.