Smoke noted over what's now Nunavut, and nobody could smell a thing. That's the part that threw me. The Chinchaga fire had been eating muskeg in northern BC and Alberta since June, left to burn because there was nothing out there to save, and by late September 1950 the pall was riding high enough over the continent that people hundreds of miles off got dim brown afternoons and a sun that went blue or lavender and no woodsmoke on the air at all.
Between 1.4 and 1.7 million hectares, which is still the largest recorded fire in North America. The Evening Star front page from the day after has it tucked in a right-hand column under the Korea banner — semi-blackout, yellow sky, mercury down to 44. Birds in the east went quiet mid-afternoon, which is the sort of thing a fire in Alberta shouldn't be able to do.
Smoke particles of roughly a micron across scatter red and yellow light preferentially and let the blue through, which is backwards from a normal hazy day. So the pall worked like a sieve with one mesh size, and you only get it when the burn produces particles that uniform. And no smell, because the whole layer was miles up.
Blue and lavender suns come from smoke particles all landing in a narrow size range, roughly a micron, which scatters red light instead of blue — the opposite of what the sky usually does. Happens after big fires and after Krakatoa. I'd have been out on the step till it got dark, dinner cold on the table.