Honeywell HPA304 Allergen Plus HEPA Air Purifier review

The white Honeywell HPA304 is the highest-capacity member of this older three-console comparison, with a published 465-square-foot room rating at 4.8 air changes per hour. It is an Allergen Plus unit with simple local controls and replaceable filters, not a sensor-led or connected purifier. The licensed Honeywell Store states that the exact HPA304 is discontinued; the review is most useful for identifying an existing machine or checking an accurately described residual-stock offer.

A real step up in area—and three HEPA cartridges

Honeywell lists 465 square feet at 4.8 ACH on the exact HPA304 page, based on smoke-CADR testing at the highest level. The cited pollutant values are 300 CFM for smoke, 320 for dust, and 300 for pollen. The single CADR number in the finder is the smoke value; the larger dust number should not be substituted. At this published repeated-cleaning basis, the HPA304 is a stronger area fit than the HPA200 at 310 square feet or HPA104 at 155. Open layouts, higher ceilings, blocked grilles, and lower-speed use can reduce practical performance, and the manufacturer does not guarantee that all room air passes through the filter.

The official Store page identifies a white HPA304, UPC 328785001693, and MPN HPA304. Some of the page's descriptive copy refers to HPA300, a related family model; use the HPA304 title, exact offer, and model-labelled feature table rather than treating an HPA300 mention as a second included purifier. Honeywell Plugged In independently lists HPA304 and the same 465-square-foot basis.

Old-fashioned controls with useful timed operation

The model page documents three cleaning levels plus a separate Turbo mode, filter reminder, 2-, 4-, and 8-hour automatic shutoff, and a panel-light dimmer. The shared HPA300-series manual explains the three normal settings and Turbo boost, filter installation, and replacement reminders. This gives a household a direct way to choose a steady setting, use the highest speed temporarily, then let a timed session stop. It is not the same as sensor-triggered Auto. Neither the manual nor product material documents app control, a particle-sensing Auto mode, a numeric PM2.5 display, or a color air-quality meter. The Store calls it quiet but publishes no dB(A) value; if a strict nighttime noise ceiling is needed, the model cannot prove it.

Plan for the larger filter set

The HPA304 uses three Type R certified HEPA filters plus one Type A odor-reducing pre-filter. Honeywell's claim—up to 99.97% capture at 0.3 microns and larger—applies to air passing through the R filter, not every particle in the entire room. The A pre-filter helps catch larger debris and reduce some everyday household odors; it is not an all-purpose gas remover, and Honeywell explicitly says the machine does not remove carbon monoxide. The manufacturer guidance is roughly one year for the R set and three months for the A pre-filter. In practical terms, the large-room rating comes with three HEPA cartridges to check and replace, not one oversized all-in-one filter. Do not wash the media; power off, unplug, remove the grille, and follow the manual's filter-tab and reset instructions. Heavy dust or smoke can shorten the useful interval.

Placement, size, and a careful buyer decision

The licensed Store lists the body at 20 × 10.83 × 22.38 inches, 17 pounds; Honeywell Plugged In gives rounded dimensions of about 20.0 inches long, 10.8 inches wide, and 22.3 inches high. These agree closely, but allow additional space for unobstructed intake and exhaust rather than planning around a tight box. The manual calls for upright use on a firm, level surface away from walls and furniture, indoors and away from damp locations. It also recommends operating with doors and windows closed for better performance. Remove protective filter wrapping before use and check that every filter is the intended type.

This is the one of the three most plausible option if your room falls above the HPA200's 310-square-foot figure and within the HPA304's 465-square-foot figure, you accept local controls, and three annual R filters are a workable upkeep plan. It does not satisfy an essential app, Auto-sensor, verified dB(A), or larger-than-465-square-foot need. Because the model is discontinued, compare an exact current Honeywell alternative by its own independent 4.8-ACH figure and filter configuration; do not infer a like-for-like replacement from a shared product-family page or a similar model number.

Sources: Honeywell Plugged In HPA304 page, licensed Honeywell Store HPA304 listing, and AHAM 2023 room-air-cleaner directory and official HPA090/HPA100/HPA200/HPA300 series manual.