/ Field knowledge · IMC 407
Map the room. Then pick the ACH.
IMC 407.1: ambulatory care and Group I-2 must meet IMC 407, ASHRAE 170, and NFPA 99 — design to the most restrictive (ACH, outdoor air, pressure, filtration, monitoring). A clinic labeled “healthcare” without a 170 room type is the comment.
Educational 2024 IMC 407. Confirm occupancy with the AHJ before ventilation design. This is not an ASHRAE 170 design or a hospital certification. This page does not invent air-change numbers. Packet: 407 PDF · ES.
- Map every clinical space to a 170 room type (OR, procedure, AIIR, PE, soiled, sterile — as the program actually is).
- On M-601: Space | 170 room type | Total ACH | OA | Pressure (P/N) | Filtration | Temp/RH | Exhaust. Not just OA cfm per person from Table 403.3.1.1.
- AIIR (isolation): negative to adjacent; dedicated exhaust (often outdoors/HEPA); directional flow clean → less clean → AIIR → exhaust; continuous pressure monitoring; fail-safe on loss of negative.
- PE (protective): positive to adjacent; HEPA-filtered supply; directional flow PE → anteroom/corridor; monitor and alarm; fail-safe on loss of positive. Do not mix AIIR and PE.
- Controls: OA tracking, alarms (low OA/ACH, pressure fail, high filter ΔP); occupied/standby modes never drop below required minimums.
Table 403 on an I-2 set
Designing a healthcare space to Table 403.3.1.1 instead of 170 room-by-room ACH and pressure is a path error that requires redesign, not a label change. Start the ICRA before mechanical design.
Source: DCT 407 · hub: healthcare ventilation · tool: occupancy check.
What to send
Occupancy (B medical office vs ambulatory vs I-2), room list / procedures, and whether an ICRA exists. Program first. ACH second.
If the set says “healthcare” without a 170 room type
Send occupancy and the room list. MasterBuild will say whether this is still Chapter 4 or already 407 / 170 / 99.
Send Project Background+1 (786) 398-6940 · osmany.portal@masterbuildconsulting.com
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