Wall vs Roof Ventilation

Hi Guys,
Just want to get your opinion on some ventilation constraints put on by our local authority.
They state that:
"Exhaust/ventilation must effectively remove fumes, smoke steam and vapours. Exhausts should discharge vertically and above the mobile."
I was hoping to have my ventilation set up on the back wall of my truck because it looks so much cooler than the eyesore that roof ventilation provides.
Do you think if I setup ventilation on my back wall that i will breach the stated requirement? Can back wall ventilation discharge vertically and above the mobile?
Thanks for your time,
Pat

Unless this is actually wrote in the locale code (which I doubt), it just some one's opinion or an HD/s uniformed  judgment.   There are conditions which make vertical exhaust (roof) impossible.   ... Ask the HD to show you the Code section.  This usually stops their argument.
 
The real problem with a horizontal exhaust, is the collection of grease (a fire hazard) within the duct.   So the duct is required to sloped for the grease to drain to a collection point; and it must be accessible for cleaning.  See the IBC Mechanical code.
 
In your situation the horizontal duct is very short, just slope it so the grease will drain back into the hood drip tray (if possible).  And, the exterior vent should be easily removed for cleaning as required.

I once heard from an old school vendor that you should never vent out the side or end of a trailer or truck. The reason was that you'd dump your grease laden air onto tents, trucks, or trailers behind or next to your operation. Supposedly if you vent up the wind would dissipate the grease and not dump it onto your neighbor.  I also like the looks of side or end exhaust vents.
Jack

Great responses guys..
 
I'll go to the source and look up the actual clauses around this within the Code.
 
I'll vent up and ensure my duct slops down so i dont dump on my neighbour and i can drain my grease to a collection point.
And still look cool while im doing so..
 
you guys wouldnt have any links to this sort of ventilation setup would you?
 
thanks heaps for the help!