ASHRAE 189.1 §6.3.2 (drift eliminators: 0.002% counterflow / 0.005% crossflow of recirculating water flow); CTI ATC-140 Isokinetic Drift Test Code

ASHRAE 170 Table 7-1

The air change rates are right but the pressure direction is backwards. ASHRAE 170 Table 7-1 requires an airborne infection isolation room to be NEGATIVE relative to adjacent spaces — exhaust must exceed supply so air flows INTO the room and is exhausted, keeping airborne pathogens from spilling into the corridor. The room protects everyone outside it from the patient. Positive pressure is what a protective environment (PE) room uses, which protects an immunocompromised patient FROM the building. The two room types have the same 12 total / 2 outdoor ACH and opposite pressure directions, which is exactly why they get mixed up. Get the direction wrong and the isolation room does the opposite of its job.

ASHRAE 170 Table 7-1 / FGI Guidelines

This passes all code requirements. ASHRAE 170 Table 7-1 specifies an OR temperature range of 68-75°F and a relative humidity range of 20-60%. The facility's 72°F and 45% RH are well within both ranges. The visible display allows the surgical team to verify conditions during procedures. The alarm capability ensures staff are notified if conditions drift out of range. The dedicated AHU with cooling, reheat, and humidification provides the three-stage control needed to simultaneously manage temperature and humidity — essential because cooling the air also removes moisture, requiring separate reheat and humidification stages.

ASHRAE 170 Table 7-1 / FGI Guidelines 2.1-3.2

This fails on multiple counts. First, ASHRAE 170 Table 7-1 requires a minimum of 12 total ACH in AII rooms — the 10 ACH provided is below the minimum. Second, AII rooms must maintain negative pressure (minimum -0.01 inches w.g.) relative to adjacent spaces, which requires the exhaust rate to exceed the supply rate — not equal it. Neutral pressure provides no directional airflow control and allows infectious aerosols to escape when doors open. Third, while HEPA filtration on the exhaust is good practice, it does not compensate for inadequate air changes or incorrect pressure relationships. The room as designed would not contain airborne pathogens.

ASHRAE 62.1

ASHRAE 62.1 requires outdoor air determined by the ventilation-rate procedure — for offices, 5 CFM per person plus 0.06 CFM per square foot — not an arbitrary fixed percentage. Run the numbers: 20 occupants need 100 CFM of people-OA plus the floor-area component (a 2,000 sq ft zone adds 120 CFM, totaling ~220 CFM). Whether '15% OA' delivers that depends entirely on the unit's supply airflow — a 2,000 CFM unit at 15% provides 300 CFM (passes), a 1,200 CFM unit provides 180 CFM (fails). A percentage setpoint with no calculation behind it isn't a compliant ventilation design.

ASHRAE 62.1 — Section 6.2 (Ventilation Rate Procedure)

Minimum outdoor air position must meet the zone ventilation requirements of the Ventilation Rate Procedure during occupied mode — it can never be 0%. ASHRAE 62.1 ventilation rates apply whenever the space is occupied, so a 0% minimum during occupancy starves the space of required outdoor air and is a code violation. (0% is only acceptable during UNOCCUPIED periods, where ASHRAE 90.1 actually encourages closing the OA damper to save energy.)

ASHRAE 62.1 — Section 6.2.5

VAV box minimum airflow must never be 0 CFM in occupied mode. ASHRAE 62.1 requires minimum ventilation airflow to each zone at all times during occupancy. Setting minimum to 0 causes ventilation code violation and poor indoor air quality.