Fresh Air to Boiler Room

I have a boiler room in a 3 family house that is enclosed by 2 hour walls and ceiling. Currently there is a window leading from one wall to a adjacent crawl space that vents to the outside. I know that I need to duct the air intake through the crawl space and of course submit to DOB. Do I need a 90 minute fire damper? Can I get away with an old memo from Dec. 21, 1977 that says a 1 hour duct is ok? The house is to be renovated so DOB will be involved one way or another. We are submitting under 1968 code.