This article is from the Model Rockets FAQ, by Wolfram von Kiparski with numerous contributions by others.
Many (most?) launch ignition systems are not 'flashbulb safe'. Just
arming the circuit (i.e., doing a continuity check) will fire the
flashbulbs and ignite the motor. If you plan to use flashbulb ignition
often, you might consider investing in a 'flashbulb safe' ignition system.
From J.COOK@ens.prime.com (Jim Cook):
A lot of launch systems use a light bulb to do a continuity check.
The current through the light bulb is enough to set off flash bulbs
(They require only milliamps to fire).
Remember that electric matches may ignite on any amount of current above
200 miliamps. Flashbulbs may ignite with as little as 50 miliamps of