There are two concepts raised here: 1)That emergency eyewash and/or showers are used infrequently and therefore the waste stream can be dealt with seldom if ever; and 2) That emergency eyewashes and /or showers are indirect waste.
I will debunk 1) first: Emergency eyewashes/showers are required to be tested weekly. When someone is exposed to a hazardous spill, you want to encourage the user/victim to properly drench their self even if it is "minor", perhaps for 15 min or so. If the fixture makes a mess every time it is activated (20 gpm for a shower), no one will ever really test them, and even worse - potential user/victims will be discouraged from using it. If there is no drain, then practically speaking, there is no emergency fixture.
For 2), all eyewashes I am familiar with either have their own bowl with a drain tailpiece that can be trapped and routed to the sanitary sewer, or they are designed to be installed with a sink. Thus there is no reason it can't be directly connected (see above if you want to bring up dried out traps). Of course, an emergency shower with a floor drain is inherently directly connected, just like a normal shower - the floor drain IS the direct waste.
