I have 30 years experience in indoor air quality. The key is ventilation/air change. You can have 100% filtration efficiency however if you don't have a good ventilation system to displace air in every corner, the contaminants will still stuck somewhere. On the other hand, if you can purge the space quickly, the contaminants might not get to you even if you don't have any filters. That's why outdoor spaces is so much safer than indoor spaces in general. But if you have a tent/shelter with well sealed envelope/surroundings, and the weather is calm/no breeze, it is likely worse than a well ventilated indoor space.

For hotel rooms, I would open the windows for a while and won't worry about virus in the air.