I didn't know how to approach this either originally. But, I'd seen the "200 LFM" specification with other cards (usually buried deep in the documentation), going all the way back to LSI SAS2008 based ones. Since the specification has been around for a while, for both LSI and Adaptec, others have posted info on how to approach it. And, being both a rule follower and copy cat , I've been cooling all my HBA/RAID cards since none of my systems have very high airflow.
The full spec as I understand it is 200LFM with the air at an ambient temperature of up to 55C measured 1 inch from the card. As @kiteboarder mentions above, how in the world do you monitor that?
From what I've read, the only component that needs the high airflow is the heatsink. So, if adding a fan onto/near the card for cooling, you only need to calculate airflow to cover the heatsink's surface area. This calculator has a circular air source option so you can try different fan diameters to determine airflow at different LFM: ENGINEERING.com | Air Flow Conversion Calculator . Besides CFM it also gives volume in m3h, which is helpful if you're looking at Noctua or other brands that use m3h instead of CFM.
Some time back, I read in posts elsewhere that, if the 200LFM requirement is for air up to 55C (which is pretty darn toasty), it would follow that airflow could be lower when the air temperature is lower. So, I've usually put a lot less than 200LFM on my cards and haven't had a problem. Admittedly, in my home setup, the sample size is pretty low.
For my ASR-71605 in a 3U chassis that otherwise ran very cool, I put a Noctua 80mm fan in a holder in the next PCIe slot over. Plugged into a PWM header, it only moves about 80LFM at its usual speed, but I had no issues with heat.