For the new high efficiency hoods,   require  an Ashrae  110  test  as manufactured(AM)   and   another one  as installed (AI) for  at least 10 or 20% of the hoods  in your facility. 

Air flow alarm  visible( with numbers)  and audible are a requirement.  When testing the hoods   we  have a required that the  hoods pass at flow rate: 80 FPM(70-90FPM) at 18 inches opening  and hood alarm set at 55FPM , sash response time at 60 sec or less.   Ask for a balancing report also to be sure the supply is proper for the space as a VAV hood  will not work without enough supplied air, hence the  constant flow alarm which can be a nuisance to the occupants.   Fume hoods sensors are not always useful  as research hoods  have to run overnight  at optimum flow rates, a constant battle between the energy group and safety people.  Room occupancy sensors are fine as long as the researchers know to not to work in the dark(with the light off)  unless they want their hoods air flow to go down.   

Again, just my two cents.