I am often asked why it is so important that all openings to an electrical box are sealed. The NEC (National Electric Codes) that are applicable in most jurisdictions require it. But why?
The picture graphically explains why. Not only is it a safety hazard for young children, but any opening invites unwanted guests into the electrical box. This picture is of a sub-panel and is from an actual inspection done by a fellow inspector. First the mouse entered the box and ended up in the lower right hand corner after being fried. A snake, in hot pursuit, followed the mouse through the unplugged hole in the bottom of the box and was also fried. Gee, no wonder the electrical doesn’t work in the garage!