Good questions, straight answers.

Two things. It filters the air in one room with a HEPA H13 cartridge, and it shows you, on the screen on the front, what was in the air before, during, and after. Smoke. Cooking gases. Dust and pollen. Carbon dioxide. Cleaning supplies. Humidity and temperature. All read in plain English.

Bedrooms and home offices. In a larger room it still works, it just takes longer to clean the same volume of air. Final coverage numbers are pending the prototype's anemometer test.

Quiet at idle, the level you have to listen for. When the air climbs and Linden ramps the fan to clear the room, you will hear it — that's the cost of actually moving air. Settles back down within a few minutes of the air clearing. We'll publish a measured in-room number once Run A is on the bench.

A normal air purifier hides the work behind a plastic shell and asks you to trust it. Linden filters the room with the same kind of HEPA cartridge — and then shows you the numbers. You see it work. You compare today's air to yesterday's. You see when something climbs, and when it clears.

About two minutes. Plug it in. Pick your Wi-Fi on the screen. That's it. No app to download, no account to make.

No. The screen on the front is the interface. If you want a bigger view, every Linden runs a small dashboard you can open in any web browser on your home Wi-Fi.

Yes. The filter runs. The sensors read. The display updates. The readings save on the device. The Home Assistant connection is the only thing Wi-Fi is for, and it's optional.

Every six to twelve months under typical use, more often if you live with a fireplace, a smoker, or a wildfire season. Linden will let you know on the screen when it's time. Replacement filters ship from us directly. Cadence and price are still being finalized for the first commercial run.

On the device. Nowhere else. There's no Threadcraft Labs server in the path. We don't run analytics. We don't have telemetry. If you want your readings on a phone, you open the dashboard in your browser. If you want them in Home Assistant, you turn that on yourself.

Linden keeps working. There is no cloud login to expire. There is no service to shut off. The dashboard runs on the device. The Home Assistant integration runs on your network. Warranty terms will be written into /terms before the first unit ships, and the warranty travels with the product if the company ever changes hands.

Dyson sells a purifier with sensors and a phone app. Linden sells a purifier with sensors and no phone app. Both filter the room. Dyson hides the readings behind an app. Linden shows them on the front. Pick whichever matches your home.

Airthings monitors air. It doesn't filter it. It also runs through the Airthings cloud and account system. Linden monitors the air and filters the room. If you want the monitor without the filter, the Airthings is the cheaper choice. If you want both in one piece that doesn't need an account, Linden is what we built.

A plain HEPA box filter is the cheapest way to clean a room. It doesn't tell you anything about the air. If you want clean air and no information, a $100 box filter is the right answer. Linden is for people who also want to see what's in the room.

Run C is twenty-five numbered units. The list opens before they go on sale. Get on the list and we'll write you once — when it opens, not before.

$429 for a numbered unit in Run C. Run D — the next, larger run — will be priced separately when it opens.

That's the plan, but it's contingent. Run D — roughly two hundred units — only happens if Run A on the bench and Run B in real homes go well enough to scale. The first twenty-five are numbered and signed; if there's a Run D, those units are made the same way, by the same hands, in the same Wisconsin workshop. We're not committing to a date.

No. Threadcraft Labs is a one-person Wisconsin workshop, funded by personal capital and a small SBA-backed loan. We are not raising outside capital. We are not trying to be the next anything. We are trying to ship one good thing well.

Warranty terms will be published before the first units ship. We are working through the term and the cross-ship policy now; the final language will live on /terms before any unit goes out.

Write us. If it's a part, we will ship the part. If it's a board or a fan, we will ship a replacement and a return label. We are a small shop. Support runs through one email address.

Linden as a complete product will be ETL listed for the US market before it ships to a paying customer.

No. Linden is an environmental monitor and air purifier. The readings are descriptive, not diagnostic. If you have a medical condition that requires specific air quality measurements, see a doctor.