How to build a DIY box-fan air filter

This Old House · Tutorial · YouTube title: How to Make a DIY Air Filter | Ask This Old House

Why it's here

HN recommends it as a practical breakdown of filtration versus air volume and a clever box-fan filter design.

What it covers

This Old House's Ross Trethewey explains MERV filter ratings and how air filtration works, then shows how to build a localized DIY air filter, including a box fan with multiple filters.