How far do you smell 3 photoperiods?

wind direction? which does swirl so at least on some days people will definitely smell it. if the people are upwind, they'll smell it less often.. if downwind it's going to be common i bet. some plants do smell more than others, but i don't think that variance is enough to depend on from just 20m even if faint... soem noses may miss it but some will definitely notice it. Early on not a ton of smell, but in flower it does get stinky once those buds form and start ripening. lavender and other strong smelling plants are often planted around yard to help mask the smell. i'm not up on that info but i bet a cursory google search will list plenty of plants that help mask the smell of marijuana... heck, there's a "Weeds" episode that lists a few good ones.