You have a good question here. The simple answer is, that you can't keep it out.
This is a judgement call. I don't want to be controversial, so will try to avoid that. In checking through the USDA extension service information and what several college culinary schools say, I have found the following consensus. They are seperate, individual statements. I just lumped them all together, when making my descision, and have made my peace with it.
1) First, most everyone agrees that bacteria can begin to grow whenever the food is in the danger zone, generally considered to be 40F to 140F.
2) Secondly, although bacteria is growing and multiples rapidly, it takes about two hours to reach the serious danger point.
3) Hot smoking would eliminate this concern, but unfortunately does not give me the results I want.
Normally when smoking, I prefer to use chunks and larger pieces of wood. (In some of my posts, for example those on fish and shellfish, I have encouraged chips) The reason for this is that I am NOT trying to COOK the food. I am simply trying to impart that great smokey flavoring, as quickly as I can, and then move on to the actual cooking method.
My rational has been that if I use chips, I generate smoke much quicker and at a much lower temp than if trying to use chunks. This allows me to Cold Smoke, or even Warm Smoke, but the key thing is that the process is over quickly. I can use chips, run a couple pans against the Pork, achieve the smokey flavor and be on to the higher, safer temps, in 30 to 45 minutes. Certainly less than an hour.
I know others may disagree. I don't want to argue with what anyone else thinks or does. I am just trying to answer your question by explaining what I do, and why. I have just made the judgement call, that If I adhere to this strict timetable, I can get into the danger zone and back out again before having much of a risk. I feel that on a compressed smoking timetable like this, the bacterial growth is minimal and rely on the actual cooking process to kill what little does develop.
Don't know if that clarifies anything, but this is what I do and the reason I do it. Good news is I have never had a problem after a lifetime of using this method.