What is in the set
Coway sells the replacement set for this unit as the "Airmega Mighty AP-1512HH & 200M Filter Set". Coway's product page says it "includes 1 HEPA filter and 2 deodorization filters for odor control"; Coway elsewhere describes the same contents as "AP-1512HH filter set(Two custom filters & HEPA filter)". The two deodorization (activated carbon) cartridges and the HEPA cartridge are separate pieces, not one combined unit. The pre-filter - Coway's stage 1, installed frontmost - is washable and reusable and is NOT part of the replacement set; Coway sells it separately as the "Airmega 200M & AP-1512HH Pre-Filter" (SKU 3105422).
Coway calls the deepest stage a "True HEPA" filter. No public HEPA certification exists that a manufacturer can obtain, so that label and the numbers attached to it are Coway's own declarations and are reported here as Coway's wording, not asserted: Coway says the True HEPA filter "effectively removes fine dust and cigarette smoke up to 99.97%", and its store page ties the 99.97% figure to particles "as small as 0.3 microns in size". Coway publishes no test method or standard behind the cigarette-smoke wording, and the percentage describes filter-media efficiency as published by Coway about its own product - not a whole-room removal rate and not an independent test result. Coway describes the other two stages as follows: the pre-filter "removes relatively large dust ... human hair, pet hair, and so on", and the deodorization filter is the stage Coway describes as targeting odor and gas.
Stack order front to back, as printed in the manual: "Pre-filter > Deodorization filter > True HEPA filter". Coway's setup support article states the installation sequence from the other end - "Install the filters in the correct order: HEPA Filter, Deodorization Filter, and Pre-Filter" - i.e. the HEPA seats deepest and the pre-filter goes in last, nearest the front cover. Both are Coway's own wording and they describe the same stack from opposite ends.
Separately from the filters, the AP-1512HH has an ionizer. Coway states it "is optional and can be turned on / off" from the panel's Ionizer button, and the manual shows an Ionizer indicator and an Ionizer button on the operation panel. Because of it, CARB lists the AP-1512HH as an Electronic air cleaning device (Executive Order G-16-011) rather than a Mechanical one; CARB's electronic category is tested to an ozone limit of 0.050 ppm. CARB certification is a legal requirement for selling or shipping a portable air cleaner into California, not a feature, and CARB itself states that certification "does not reflect air cleaner effectiveness or 'health safety'". Replacing filters does not change the ionizer; switch it off at the button if you do not want it.