Gas grill: soaked wood chips vs. dry wood chips

If you're putting your wood chips directly on a fire, it's good to soak them (and that means real soaking--a few days--not an hour or two). This prevents the wood chips from actually catching fire, which can cause off flavors from combustion chemicals settling back on your food. Tastes kinda like a brand new telephone pole smells on a hot day. Tar/Creosote, and not a nice flavor.

But on a gas grill, if you've got your chips in a pan or wrapped in a fairly tight foil pouch, you needn't worry so much about the chips actually catching on fire. As long as they just smoulder, you're good to go.

You want your wood to smolder/smoke, not burn. This is why soaking chips is recommended. However, the effect gained from that practice is temporary. Once the moisture boils off, your chips will catch fire in the high oxygen environment of your gas grill. I recommend choking the oxygen supply to your smoke wood, and placing the chips so that less heat gets to the wood (you want just enough to get the wood to slowly smoke). A foil pouch or smoke wood box would do the trick.

Don't soak the chips for a gas grill. Get a large aluminium pan and place all your chips in it first. Then heat up your grill and get them smoking, but not on fire/combustion this is bad. Once you have a good smoke going, put your pork shoulder in there. After a while the chips may try to catch fire but you can prevent this by watching them closely, through the holes in your grill you don't want to open it too many times, and dousing or spraying any flame ups with a small amount of water as some people like to do with a charcoal grill. Follow this method and you will never cook your pork shoulder any other way!

Actually, there is no reason to soak the chips at all. The wood doesn't absorb enough water to make a diffrence in either smoke production or length of cooking. That said, if you are looking to create a more distributed smoke over the cook cycle, adding water to the pie pan that holds your wood chips will create the same effect that people are trying to accomplish with the soaking. The one caveat is that you have to put the pie pan directly on the burner in a gas grill, as the grate will not be hot enough at 200*F to produce the required heat.

The best practice would be to separate the wood chips from the fire altogether. Use a small aluminum tray or just a bit of aluminum foil, to hold the wood chips near the flames. The idea to smoking is to cook "low and slow" but you only really need the wood chips for the first hour or so, additional smoke after that point doesn't really add more flavor.

This website has a nice explanation for smoking ribs on a gas grill. The principals apply to a pork shoulder just as well.

Personally, I have watched the wood chips opening my stainless steel smoke boxes on occasion to see "what's going on". My experience is that soaking the chips is a waste of time. There will be a little bit of steam for awhile, but the chips don't start smoking until they have completely dried out anyway. Best advice I can give on this is limit the oxygen flow in your smoke boxes. Mine have holes on bottom and on the lid, I cover the bottom holes with foil before putting the chips in and this helps in most cases, although I still get flame ups some times. I've found putting more chips in helps with flare ups, rather than soaking as many will say. I have had chips catch fire regardless whether I soak them or not. Fire needs oxygen... restrict it's oxygen soaking it only takes longer to start smoking.

The trouble with soaking is that it takes longer to get them to start smoking (you're just drying them out). This makes timing the start of smoke with putting your meat on more difficult. On top of that, you're using more gas to dry out the chips to start it smoking, which is where you started from!!