I have had this happen in past in a stick house, the trap itself was really grungy, needed taken apart and cleaned well. As c5racer stated, there is a water trap of a couple of inches that keep the odors out, just like in your home. In some commercial spaces, they don't run enough water in the drains, (like in a storage room) then they dry out and stink. Also, If you have a clogged vent, the water will get sucked out of the traps at times as well.
Ozz
'07 3400RL 2nd RTU
2 Golf Cart batteries 1500 watt inverter
Honda 2000 Generator, 2nd one and twinning kit coming
Maytag's with 220 Dryer
Stationary domed Sat. dish
LCD 12 Volt Amp gauge
LCD Tank Monitor
3 added 120 volt outlets
On Board Air; 12 Volt Viair 450C compressor
2006 Ford PSD 4x4 Off Road Lariat
Hadley Air Horns
Truck inverter with 110 volts for laptop
Color Backup Camera
Awning lock
