First thing, don't soak your smoke wood if you have in the past...it just delays the onset of smoke until the water evaporates. Wood will smoke white until the natural moisture dissipates...even when dry/cured it still has water from the humidity in the air, as well as a small amount of volatiles in the wood. After the initial white smoke (could take 5-10 minutes) it should thin out to a light blue smoke. If a heavy smoke is continuous, too much heat and/or air is getting to the smoke would causing a faster ignition.
Controlling smoke in vertical gassers:
(1) Use a combination of chips and chunks...chips will smoke sooner, burn faster and won't last as long. Chunks take more time to start smoking, burn slower and last longer.
(2) If high burner is used during cold weather or for higher smoke chamber temps such as with poultry, this may cause excessive heat getting to the smoke wood. You may be able to offset this by elevating the smoke wood box/tray with a simple mod in order to increase the distance from the heat source.
(3) Another option to reduce heavier smoke is to limit the amount of air/oxygen available to the smoke wood by using a metal can (cut-down to necessary height to fit under water pan, if needed, and burn-out the can and lid to season it before using in smoker) with the top cut out by an old-style can opener...save the lid and use to drop onto the can if smoke is still too heavy. You may need to punch a couple small holes into the side of the can to allow a small amount of air to enter if the smoke too light. This works best with chips, as chucks are more difficult to fit much into the can and because of less surface area, they tend to burn too slowly when put in a enclosed container, but could be made to work.
(4) A foil pouch can be used to put smoke wood into, folded over the wood to fully enclose (some poke holes in the foil to regulate smoke output...this will limit the smoke in a manner similar to using a metal can with the lid dropped in onto the wood...smoke will be very light.
When using my vertical gassers, I like to have charred smoke wood in the pan/bax after 5-6 hours...if it burned up to ashes, I likely had to much heat and/or air getting to the wood. With my old GOSM 3405-GW, I always used to cover on the chip box and had charred wood in the box with very little ash. My Smoke Vault 24 has an open cast iron tray, so using a chip/chuck combo works very well to produce a rapid onset of smoke and a longer smoke time without flare-ups of smoke wood. I can leave my old charred wood chunks on th etray from the last smoke and just add fresh when I fire up for another smoke...the charred pieces eventually burn up to ash, but this takes at least another 10-12 hours of smoker operation.
The main things to remember about smoke wood is that not enough heat or air produces little to no smoke. The opposite is too much heat or air produces a heavier smoke, a faster burn and less smoke time from your wood. A few small chunks can last for 6-8 hours if properly regulated, and chips can be crowded into a smoke box with lid and last for 4-6 hours as well. My old GOSM loved a full smoke box when using chips, and sometimes I only needed to slide the cover to the side to let a bit of extra air in after the first 3-4 hours to keep it smoking light for a all-night butt smoke.
BTW, keeping your exhaust vent open is doing the right thing. If you want to do a little light mod work, you can bend the tabs on the side intakes to reduce draft for a bit better fuel efficiency. My Smoke Vault performs better with no side intake draft...less grate temp variances from side to side, front to back, corner to corner, and top to bottom...depends on the smoker, but some don't like that cold air rushing in from above the burner.
Hope this helps you find that sweet spot...where the smoke is moderately light, steady, and log lasting.
Come on back if I can be of further assistance, or if you have any questions about my explanations.
Eric
