NFPA 820 - Air Changes for Recirculation of Exhaust Airflow?

[SB7685]

NFPA 820, if one was to explore using recirculation for an unclassified space, would you need to use no less than 6 air changes as stated in section 9.3.3, or would it be OK to to use NO ventilation requirement, as stated in Note (1) of Table 6.2?

Note (1) of Table 6.2 states "The NR designation (no requirement) in the ventilation column indicates that NO ventilation requirements are established for the space, and therefore, Table 9.1.1.4 also has no requirements."

Section 9.3.3 states "Recirculation of up to 75 percent of the exhaust airflow rate for unclassified areas shall be permitted, provided that the following criteria are met:
(l) The recirculated air and outside airflow rate total is not less than 6 air changes per hour.
(2) Recirculation does not occur during occupancy.
(3) Recirculation does not occur whenever a combustible gas detector senses.

Any feedback would be much appreciated, thanks!

 

[cry22]

Why use Table 6.2? From what I can tell, Table 6.2 is for solids treatment spaces, which is Classified space.

9.3.3 is for unclassified space - and you should use it.
Unclassified space is for dry well - the recirculation requirement is in there for winter operation so you can heat the space without bringing 100% OA, but you need air motion at 6 ACH.
the rest of the year (above 50F) you are in 100% OA ventilation mode.

Why would you go with no requirements? you're shooting yourself in the foot.