What do I do if I still smell something and I am using a Vent-Sure Downdraft kiln vent?
First, all the peepholes must be plugged, the lid adjusted properly, and any other holes into the kiln plugged as well for the vent to work properly.
There is a sliding piece of metal on the by-pass collection box attached to the bottom of the kiln stand. This sliding metal piece covers a hole. If you can smell fumes, be sure the hole is covered up by the metal slider. While you are under there, be sure the flexible aluminum vent pipe is in place all the way around the connection point to the by-pass collection box under the kiln. A large open place in the ducting can allow the kiln to leak fumes into the room. Follow the flexible aluminum pipe all the way to the vent motor inspecting the pipe the entire way for holes or tears. Inspect how the pipe connects to the motor.
If the kiln is cold and off check the holes in the bottom of the kiln. Should be roughly one 1/4" hole for every 4 cubic feet of kiln interior- up to 5 holes. Poke something all the way through the holes. Maybe a brick chip or the stand not centered under the brick slab can plug a hole.
Next, go out to where the motor blows the fumes outside. There should be a good amount of air coming out. No open windows or intakes should be close to the fan outlet or fumes can just come back in. Motor is loud and it vibrates a bit.
With clay or glaze in the kiln, it would begin feeling moist and then stinky warm air would come out the vent. It is possible to have lots of organics in the clay, or too much wax resist or use paper or styrofoam armatures so that when that stuff burns off, it can overwhelm the vent system. Using lots of wax/ paper/ styrofoam is really bad for the elements. Sometimes, in extremely heavily loaded kilns in general, it is possible to overwhelm the vent system at the highest temps.
In the test fire or in an empty kiln firing, there is not really anything in the kiln to stink or make fumes of any kind. Only smells would be the initial smell of soap and oils burning off the new elements- at most a very little smoke for about 6 or 7 seconds- most would go out the vent. As the kiln gets hotter- if it was left open before, any dust inside will burn off, and all that should go out the vent. Hotter, and any dust that may have settled on the outside could start to cook off. That would not go out the vent- so that would smell.
If it smells like plastic, or just 'funny/ wrong'... turn it off and try to locate the source of the smell before continuing to fire. As always, but especially if you think there may be a problem, monitor the kiln carefully.