Exposure time, physical proximity, air flow, amounts of saliva droplets in the air (i.e. is the The Plague Person breathing through their nose gently with a mask on or shouting at the top of their voice in full spittle-spray Alex Ferguson mode about why masks are useless). Those are the risk factors as I understand it. So if someone walks in without a mask and you tell them to fuck the fuck off ASAP, you're probably OK.
Short exposure has not been shown to be very risky. It's only prolonged exposure that appears to spread a sufficient viral load. The usual exceptions prove the rule.
Exposure time, physical proximity, air flow, amounts of saliva droplets in the air (i.e. is the The Plague Person breathing through their nose gently with a mask on or shouting at the top of their voice in full spittle-spray Alex Ferguson mode about why masks are useless). Those are the risk factors as I understand it. So if someone walks in without a mask and you tell them to fuck the fuck off ASAP, you're probably OK.