In Spain we have a similar exam and unfortunately I know that there are indeed people that cheat. I don't know the details but there are ways to make their car emit less smoke only that day, and then go back to "normal".
Probably we should do as many Asians do in this, and make it normal to go out with a face mask.
Not sure what kind of masks have to be used to effectively not breathe pollution, and their effectivity, though. Getting informed about that is in my to-do list.
Filtering airborne particulates is pretty much the baseline reason to use masks ¯\_(ツ)_/¯
(However surgical masks aren't meant to do that, they're only meant to catch things expelled from you, not the other way around. So I guess your interjection is somewhat correct in that running around with a surgical mask does pretty much nil to improve the quality of the air you inhale.)
Doctors also have masks to protect them from external things (for example, when they deal with patients that have tuberculosis), although I've just learned from Google that they are not technically called masks, but respirators (N95 respirators).
They are quite uncomfortable to wear, though. You can breathe just fine for extended period of time but it feels (at least to me, a layman in these things) like you get less air. I wouldn't wear it as an everyday thing.
I have no idea if there are more comfortable solutions that can handle pollution.
I'm a hobbyist woodworker and so I wear a half-mask with either a simple flat P3R filter [1] or a bigger A2P3R filter stack [2] a lot when doing that. When it's hot it is a bit annoying that sweat and moisture tends to condense in the mask. Another annoying thing is that these kind of masks tend to put pressure on the nasal bridge which gives you similar issues like a poorly adjusted pair of glasses. This is a larger problem with the filter stack because it is much heavier than the flat filters.
As for efficiency, I found a paper (DGUV IFA 0233) saying standard P3 particle filters are highly efficient even against ultrafine aerosol particles (particle diameter below 100 nm); for "larger" stuff (PM1 and larger) these are specified to remove more than 99.9 % of them.
This actually leads to P3 filters already removing a lot of smells, e.g. when you machine steel or wood, sand wood or grind steel, you don't smell it. However, gaseous stuff like solvents get through. That's what the A2 filter is for.
I've worked in one and I got used to it, wearing it for an hour at a time for 4-5 hours per day. For comfort, a positive pressure air purifying respirator (PAPR) is preferable but looks like you're on a biohazard scene.
Probably we should do as many Asians do in this, and make it normal to go out with a face mask.
Not sure what kind of masks have to be used to effectively not breathe pollution, and their effectivity, though. Getting informed about that is in my to-do list.