Would casting Clean Air on an area also remove all scents, thereby disabling scent tracking?

I would think it could increase the TN's (+2-+4) but I'm not really sure. Good question.

I'm also kinda wondering about the Physical Mask spell in this regard. Can it be used to eliminate someone's odor completely instead of just changing it (maybe changing it into something that's "unsmellable/odorless")?

Without reading the spell description, my first thought is making the pluses to TN equal the force of the spell.

If it came up I would treat it just like Sterilize for scents instead of material links. Physical Mask would work just like any other illusion for any other sense. If the target defeats it, they detect the real scent otherwise they detect what the spell is trying to fool them into think it is.

For that matter, I guess Sterilize would help foil Scent Tracking to some degree.

I generally add the Force of tracking defeating spells to the TN (for scent Clean Air and Wind seem appropriate). Also, one can have a spirit with the concealment power use it against the trail, IMO.

No, I would not allow the use of Clean Air to foil scent tracking. The Air is Clean even with the scent in the air. What I would allow is the use of Concealment to counter scent tracking or Sterilise for Scent Tracking by dogs/animals.

So I presume you wouldn't allow Clean Air to clean the air of pollutants and otherwise do its job at all then, eh? Especially since scents are just another type of chemical floating in the air.

Depending on how you look at it Funk. Are pollutants part of Clean Air? Climb the Alps, smell the flowers, is the air clean? Or is your defination of Clean Air: Scrubbed, Sterilised, and absolutely Squeeky Clean Air?

To me, as long as there isn't any harmful materials (oh, oxygen is harmful in large quantities) in the air, then that's Clean Air.

Considering the spell's description specifically states that it's clearing all impurities out of the air, leaving it completely clean, yes, I would say it's on the same level as sterilization and squeeky clean. In fact one of the examples it gives for Clean Water is that it clears up muddy water -- but by your definition, it wouldn't have done anything since muddy water is completely natural and normal.

So define impurities.

I define clean, pure air as 20.96% pure oxygen, 79.0% pure nitrogen, and 0.04% pure carbon dioxide. Just like I define clean, pure water as 100% dihydrogen monoxide. Anything that contaminaints that purity is, by definition, an impurity. Yes, that includes natural substances. No, that does not include metahumans (common sense, gotta love it).

Other impurities include, but are not limited by, natural body odors, perfumes, dust, methane gas, and Neuro-Stun gas.

And, as previously mentioned, if it did come up I would treat the situation just like the Sterilize spell except that instead of affecting material links, it affects scents lingering in the air. That means every success (to a maximum of the spell's Force) on the Spellcasting Test adds +2 to the TN to detect a given scent present in the air at the time of casting.

Blood is contaminated water.

And there is a fine version of clean water that works on metahumans, its called manabolt + special effect.

One of the things I really liked about champions is that is concentrated on what stuff actually did, then added the special effects.

While the clean water can be used indirectly to kill people (like changing their water based medication into water, or whatever) it's not going to blast that pesky HMG troll out of existence.

Chemically pure and idealistic are two different things. Considering how rarely SR magic deals with chemical definitions, attempting to make those spells conform to a system that is not used elswhere is inherently flawed. The situation that causes the most confusion is that idealized material is different in different locations. In the human citrculatory system, blood is the proper representation of water, so trying to cast clean water in a person's veins will not be harmful. In a river, the idealized is typically clear, but capable of sustaining life. In a public swimming pool, the idealized is heavily chlorinated. So, although I would argue that certain evidences of your passing would be removed by the proper clean spell, that would not include your scent in an area that has many animal scents. By contrast, in a "clean room," the spell would remove all evidence in its reach.

Oh, Clean Air. How useful that spell would've been at my last gaming session. The chairs were alive with the sound of ass-music last night. The air was seen to burst into small fireballs around open flame (like cigarettes) where the methane cooked off. The culprits wondered aloud what they ate that made them so noxious.

That question was decisively answered for one lord of thunder. As the fumes hit me full force, I had to agree: it was definitely his McDonald's breakfast. Though putrescent, the origins of the reek were undeniable, an egg mcbiscuit.

I could have kept the observation to myself, but one gamer was weak of stomach and already nauseated by the fumes. And so, quite in a sadistic mood, I shared my findings, much to the laughter of the two other gamers, but the thought of being able to identify the odor of reconstituted scrambled eggs after an intestinal passage sent the sensitive one over the edge. He left the room literally retching. Upon his return, he did say:

"Alright, change the subject. I just had to swallow my own vomit three times to keep from puking on the carpet."

And much hilarity was had by all (even though the gamer was being serious about the vomit), but the Clean Air spell still would've been most useful.

Next time just summon a hearth spirit and have it open a window, if a window is not available youc an ask ti to make a window...