How many tests per square foot?

Samantha, look in the Step-by-Step Guidance section of this credit, under Opt 2 Air Testing:

STEP 1. DETERMINE AIR-TESTING LOCATIONS
Select testing locations with the least ventilation but the greatest concentration of VOCs and other
contaminants. Testing must be completed by an appropriately accredited professional. Use current
versions of ASTM or ISO methods. The number of testing locations depends on the size of the building
and number of ventilation systems but must include all occupied spaces. If sampling is used, all space
types must be represented (e.g., office and classroom). Use the following methodology to determine how
many air testing locations are required.
·· Test at least one location per ventilation system for each occupied space type. There must be a
minimum of one test per floor. The locations selected for testing must represent the worst-case zones
where the highest concentrations of contaminants of concern are likely to occur.
·· For offices, retail, schools, hospitality, and multifamily residential projects, test areas no larger than
5,000 square feet (465 square meters). For warehouses or large open spaces in other building types
(e.g., ballrooms in hospitality, gymnasiums in schools), a limit of 50,000 square feet (4 654 square
meters) may be used. If there is evidence that the air in the space is well mixed and sources of
contaminants of concern are uniform, project teams may test a single location in that space.
·· Determine whether the project includes spaces (e.g., offices, school classrooms, or multifamily
residential units) that are identical in their construction, finishes, configuration, square footage, and
HVAC systems. Project teams may sample identical spaces by testing one in seven. If the sampled
space fails the test, all seven must be tested.

Hope that helps.

Hi Emily, thanks for the helpful info about sampling.  I can't seem to find the document with Step-by-Step Guidance that you've pasted in your reply.  I looked in the LEED NC v.4 credit manual PDF and also at the credit language reproduced on LEEDUser here, but I don't see the text that you're referring to.  Thanks!

Hi Brian - It is on page 689 of the LEED v4 reference guide. 

Thanks, Umesh!