- On hotels, it's not clear whether or not they filter the air. Generally the windows in the rooms are sealed, thus the air is recirculated. The good news is that the pollutants are largely kept outside except for whatever makes its way up the elevators.
- On walks, use your judgment. Note that the public school system will not conduct any PE classes/exercises whether indoors or out at the 200 level and above. Regardless of rating, Singaporeans are still going to work and taking the MRT. This is significant as half of the MRT system is above ground.
- Locals do wear masks, out of an abundance of caution. The most protective ones are 3M N95 masks. These are reasonably available - I did a fast check in my neighborhood and found that Guardian and Unity drug store chains, and Fairprice supermarkets sell them singly right around the registers. I presume the other drug store and supermarket chains will have them as well.