That airflow chart you posted is only referring to open hoods. For those using air cooled hoods, use the formula 3.16*(total HID watts)/20-30. The venting 101 guide says a 20-30 temperature curve for air cooled hoods but i would round up to 30 because for a 1000w that leaves you with 105cfm which should be more than enough airflow in a sealed hood. A 6'' blockbuster hood is about 4 cubic square feet sealed. 105cfm/4cf is 26.25 exchanges a minute. That should be fast enough right? I'm not really sure! I am still waiting on my equipment to get delivered so i can test this out. Ou8aCracker2, whats your take on the formula for air cooled hoods?