What's actually in your air.

The AQI app on your phone tells you what's outside. It can't tell you what's in the room you're standing in. Linden can — and it does something about it.

Linden is the piece on the nightstand that knows. It tells you, on the screen on the front, that smoke is at six times your baseline. Then the fan picks up, and over the next forty minutes you watch the number come back down.

A purifier that doesn't tell you what it found is a fan in a plastic box. A monitor that doesn't do anything about it is a number that makes you anxious. Linden does both — in one piece, made to live on your nightstand.

The screen on the front speaks plainly.

It will say the air is clearing, or stuffy, or something's burning, or nothing at all when there's nothing to say. Trends, not alarms.

What Linden tracks, in the language you'd actually use:

• Smoke. Wildfire days. Candles. Anything burning.
• Cooking. The number that climbs when you sear something on a gas burner.
• Dust and pollen. The seasonal allergy numbers.
• Stuffy-room CO₂. Rises in a closed bedroom overnight; falls when you crack a window.
• Cleaning supplies and paint off-gassing.
• Humidity and temperature.

A HEPA filter, the high-grade rating.

HEPA H13 — the rating used in surgical and clean-room filtration. It catches the small stuff: wildfire smoke, cooking soot, dust, dander, pollen, the size of particles that go deepest into your lungs.

When the air picks up, the fan picks up. When the air clears, the fan settles back down to a level you'll have to listen for. Replacement filters ship from us when it's time. We'll be honest about the cadence and the price; both are still being finalized as we get the first commercial run together.

Quiet at idle; you'll hear it when it works.

Most of the time, at the low end of its range, you will have to listen for it. When the air climbs and Linden ramps the fan to clear the room, you will hear it — that's the trade-off for actually moving air. It settles back down within a few minutes of the air clearing. We'll publish measured in-room sound numbers once the prototype is on the bench.

Real walnut, hand-finished.

Real walnut, hand-applied over a structural shell. Real wood, real grain, an oiled finish that gets warmer with age. Linden is meant to be a piece of furniture as much as a piece of hardware — and we've designed it to be openable, so that if something does need attention down the road, it can be cared for instead of thrown away.

Warranty terms will be written into /terms before the first unit ships. Linden is built to live with you for the long haul.

Setup is plug-in and pick a network.

Plug it in. Pick your Wi-Fi on the screen. No app to download, no account to make, no onboarding flow. We'll quote a measured setup time once Run A is in hand.

The screen on the front is the interface. There is no required phone or tablet. If you want a bigger view of the history, every Linden runs a small dashboard you can open in any web browser on your home network.

Linden does not phone home. It does not collect telemetry. There is no Threadcraft Labs server in the path — your Linden works on its own, without us. Home Assistant compatibility is on if you want it; off by default.