Corsi-Rosenthal Box Wildfire Smoke Guide: Prepare & Protect

The quick version covers the basics; this is the full before/during/after guide.

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Before smoke arrives

Have a box built and spare filters in. Fit fresh filters if a smoke event is forecast, so you start at full capacity.

Seal the room, run high, and keep the box central. In a large space, add a second box or use a high-output kit.

Smoke loads filters heavily — inspect and likely replace afterwards. Vacuum surfaces and wipe the fan.

Health guidance for smoke sensitivity: smoke allergy resource.

Frequently asked questions

How do I prepare a CR box for wildfire smoke?

Have a box and spare filters ready, and fit fresh filters when a smoke event is forecast so you start at full capacity.

Do I need to replace filters after a smoke episode?

Often yes — smoke loads filters heavily. Inspect them afterwards and replace if airflow has dropped or they look loaded.

What if my room is large?

Add a second box or use a high-output kit — one small unit can't keep a large, smoke-flooded room clear on its own.