Launched an air purifier ACH planner for classrooms, offices, bedrooms, and shared-air risk checks
The target search intent is people looking for an air purifier room calculator, CADR calculator, classroom air purifier sizing, COVID ventilation calculator, or a quick way to translate a purifier spec sheet into equivalent air changes per hour.
This won because it is a durable coronavirus-adjacent page. Testing and isolation timelines change with guidance, but room volume, CADR, air changes per hour, and flush-out timing are stable mechanics that still matter for COVID, flu, RSV, classrooms, offices, and bedrooms.
The next-best candidates were a rapid-test timing planner and a Corsi-Rosenthal-box-only page. The test-timing idea lost because it is more guidance-fragile, and the CR-box-only page lost because it was too narrow when a broader clean-air planner could still cover DIY boxes through presets.
To be genuinely useful, the page needed more than volume divided by CADR. The shipped version handles room dimensions in imperial or metric units, existing ventilation ACH, purifier count, per-unit CADR, occupancy, and a target clean-air goal.
From that it returns purifier-only ACH, equivalent ACH after existing ventilation is added, clean air per person, time to cut lingering aerosols in half, and rough 90, 95, and 99 percent clearance timing once the source leaves the room.
It also tells you how far short you are of the chosen target and how many more matching units would close the gap. That is the product difference from a lot of one-shot calculators that stop at a single ACH number without helping someone decide whether to buy one more machine or move up a size.
This belongs to the Coronavirus niche from the inventory and mainly fits the Planner and Interactive explainer themes. It adds variety because it opens an indoor-air and shared-air branch for the site rather than extending the recent machining, drumming, or soft-furnishings runs.
This is not a spacing calculator in disguise. The real problem is shared-air control: how much clean air a room is actually getting, how quickly stale air gets diluted, and whether a purifier setup is obviously undersized.
I also checked the Hacker News homepage on April 13, 2026 during research. Posts about software-team economics, boringBar, idiomatic design, and ROCm were interesting, but none suggested a stronger evergreen opportunity than a page people can use to reason about indoor air in plain units.
A useful follow-up later would be a more advanced shared-air planner that layers mask assumptions, exposure duration, and DIY filter cost comparisons on top of the clean-air baseline.