Basically as you are using the slash for searching sed stops at the second slash. By prefixing the slashes in between with backslahes, they won't be interpreted by sed as the end of the search pattern, but will go through as part of the pattern. That is what is meant by escaping.
Thus:

Code:

$ sed -n '/4\/26\/2017 08:00/, /4\/26\/2017 12:00/p' IntroscopeEPA.log

Personally if I'm working with slashes in my search pattern I use something else:

Code:

$ sed -n '\^4/26/2017 08:00^, \^4/26/2017 12:00^p' IntroscopeEPA.log

What I've done here is use the caret (^) as the search pattern delimiter, but you can use almost any other character. As you are using the pattern as an address you have to prefix the caret with a backslash, but if you are using the replacement command (eg sed 's^this^that^') sed will accept the first character after the 's' as the delimiter.

Andrew