Will carbon tax be applicable to other emissions?
The recent Canadian carbon tax law is just CO2.   

CO, which you asked about, is bad for people and considered a pollutant.   Efforts to reduce CO have been underway for decades including carbon monoxide detectors in homes and garages and catalytic converters in cars.  The target behind CO is elimination as much as possible.   Being a pollutant, there's a different approach.  The tax is only meant to discourage CO2 production, which isn't a pollutant, but it is a problem due to gradual build up.

Likewise, sulfur pollution, coal being a primary source, is dealt with by strict limits (in the US), and scrubbers which catch sulfur emissions have been installed in coal plants since the 1980s. 

Additional greenhouse gas taxes like CH4 might eventually come to pass, but, like CO, the effort with the greehouse gas CH4 should be elimination, not taxation.  It's also harder to put a number on CH4 released, which can be released by fracking seepage or cow burps primarily or by escape from thawing tundra (are we going to tax teh ground?).    CO2 is easier, for example because we know how much CO2 is produced per gallon of gasoline, for example, so a tax is straight forward, but cow burps or fracking seepage could be estimated so a tax there might be possible.      

But the general idea, is that, if it's preventable and a pollutant of some form, then regulation should aspire to reduce output, even strive towards elimination.   CO2 is an inevitable byproduct of burning fossil fuels, so it can't be eliminated and it would be problematic to try, but it can be financially discouraged by taxation.