I understand there is concern about releasing tiny amounts of refrigerant into the atmosphere. i think the amount that stays in the hose is a relatively small quantity to worry about for the FIY guy. Maybe it's illegal but so is going 5mph over the speed limit.

I took a quick scan of the MVAC 609 test. Here is what i found under:
"Recommended Service Procedures for Using a Manifold Gauge Set"

<<1. High-, Low- and Center-Service hoses must have shut-off valves within 12 inches (30 cm) of their service ends. These valves must be closed prior to hose removal from the air conditioning system. This will reduce the volume of refrigerant that would otherwise be vented to the atmosphere.>>

It says RECOMMENDED which may have some legal ramifications. Maybe I won't get into trouble with the law after all?

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1972 450SL
1982 300D Turbo