Here are some additional comments and tips from Ira Perlow who recently built three of the circuits:

After building the timing circuit based upon the 4528 IC, here is some additional info that you might want to add.

1. Don't route wires anywhere where they may touch the heater or the metal pipe going from the pump motor to the heater. These get very hot and you don't want the insulation to burn. Make sure that they can't fall onto these hot surfaces at a later time by shaking or melting.
2. Make sure you insulate (I use heat gun glue alot of the time) the 120 volt transformer AC leads and the relay contacts on the top and bottom of the circuit board and anywhere they would be exposed.
3. The 4528 IC circuit cycle time is the length of the space plus pulse width added together.
4. I mounted my circuit board on the bottom inside of the fogger as there was room, heat rises away from the board (and thus might affect the circuit's reliability in a positive way), and it allowed easy removal of the cover. I used standoffs for the circuit board, as well as for the transformer. The transformer was mounted in the front inside of the fogger next to (but a good 1/2" or more away) the heater.
5. Since my relay contacts were in parallel with the remote cable switch, I can use the remote to give some extra fog if needed to supplement the fog timer.

My fog timers (3 foggers) are working great and hopefully will see a full-up test at my son's school's Haunted House this coming Halloween season (and my home haunt on Haloween Night!) Regards, Ira