What you really need is a NEMA (National Electrical Manufacturers Association)
enclosure. Check your local area for a NEMA office that can make
recommendations.
The two big issues are heat and dirt. To keep the dirt (air-based carbons and
oil from diesel trucks) out of the system requires filters that restrict the
airflow. Reduced airflow equals increased heat, which reduces the system's
life span. Without filters, the soot gets into the fan bearings, slowing it
down and increasing heat.
Adapting the AppleCD SC to these conditions results in the same sorts of
problems.