I put a pork shoulder in this morning at 7:10, adding a second wood tray of hickory/apple. Had started a wood tray at 6:15 as smoker warmed up. At 1:15 it appeared it was still smoking, with a nice continuous thin column of what I took to be smoke. I finally opened the smoker to insert thermometer and check the wood tray. There was only a smattering of white ashes in the tray. What was I confusing with what I thought was smoke? I'm in Pennsylvania and it was 0 degrees when I started and is now 15 degrees. I'm smoking at 230 degrees. The stuff coming out of the vent looked exactly like the smoke did earlier in the day. It's doing it again after my open-door probing. Now I wonder just how long the meat actually took on smoke. Is this an anomaly or a routine occurrence?