Jon Lung rigged up some small fans inside his homemade face shield to defog the mask while riding in winter. On Instructables he writes:
Looking for a way to protect my face from harsh winter conditions, without enduring damp scarves pressed against my mouth or the excessive, mummy like, wrapping of my head, I created headgear with a magnetic visor that is defogged by tiny 5 volt fans.
This instructable will guide you through the process of making a Mk. 1 Winter Face Shield. As a fair warning, it is an involved project that involves programming, sewing, and some various fabrication and building. This process is much easier if you have access to a shop space with tools like table saws and belt sanders. If all you have are some hand tools and a back porch to work in, various details can be scaled to fit your capabilities. We can still do this.
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