Answer: ....
Dust and debris can cause performance deterioration.
Explanation:
Dust is a problem from the standpoint of blocking fan vents, or, if deep enough, actually insulating parts, causing overheating, but unless it contains substantial amounts of corrosive or conductive material (in which case you shouldn’t be breathing it), it won’t damage the electrical components (beyond any overheating damage).
What could happen, in some circumstances, is condensation inside the box, mixing with dust and creating a conductive sludge. This would generally only occur if you bring the box in from an extremely cold environment (below 0C, roughly) into a humid indoor environment. The protection from this is to wrap the box tightly in plastic before bringing it indoors, and leave it wrapped for a couple of hours, while it has time to warm up.
