Proposed CMC Table 4-C Cuts Clinic Exam Rooms From 4 to 2 Air Changes

Here's a fact that catches people off guard: today, a general exam room in a California licensed clinic is ventilated to the same table as a hospital inpatient room. Every OSHPD 3 licensed clinic — and those are plan-checked by the local building department, not HCAI — sizes its mechanical system off Table 4-A in Chapter 4 of the California Mechanical Code. A general exam room there needs 2 outdoor / 4 total air changes per hour. That's about to get lighter.

HCAI's final express terms for the 2025 Intervening Code Cycle (OSHPD 05/25, CMC Part 4) went to the Building Standards Commission at its August 25–27, 2026 meeting. They add a brand-new Table 4-C — "Pressure Relationship and Ventilation Requirements for Licensed Clinics [OSHPD 3]" — built on ASHRAE 170-2021, Table 8-2, with California amendments.

One caution before you redesign anything: nothing is final until the Commission records its action. A proposal can be approved, disapproved, sent back for study, or approved as amended, so verify the recorded vote before you rely on this. If approved, it publishes as a supplement (the blue pages) to the 2025 Title 24 and takes effect July 1, 2027. For why this whole supplement is thin, see our AB 130 note.

Which clinics move, and which don't

New Section 407.3.1.1 does the routing. The load-bearing sentence:

"Clinics compliant with California Building Code Sections 1226.6, 1226.10, 1226.11 and 1226.12 and licensed pursuant to Health and Safety Code Section 1204 shall have ventilation systems designed and balanced as shown in Table 4-C."

So four clinic types move to the lighter table:

• Primary care (CBC 1226.6)
• Rehabilitation (1226.10)
• Alternative birthing (1226.11)
• Psychology (1226.12)

Everyone else — the code's "other licensed clinics" catch-all — stays on hospital Table 4-A. That's surgical clinics (1226.8), chronic dialysis clinics (1226.9), and outpatient clinical services of a hospital (1226.5). Don't move those.

The cuts that matter

For the clinics that route to Table 4-C, three everyday spaces get meaningfully lighter:

• General exam room: 2 total ACH (was 4 under Table 4-A).
• Physical therapy individual room: 3 total ACH, no pressure requirement (was 6 ACH at negative pressure).
• Housekeeping room: 6 total ACH (was 10, still negative).

Verified against the current Table 4-A in the California Mechanical Code and the OSHPD 05/25 final express terms (new Table 4-C): exam room 4→2, PT 6-negative→3-no-pressure, housekeeping 10→6.

Fewer total air changes mean smaller air handlers, less reheat, and lower fan energy on a primary-care, PT, or behavioral-health tenant improvement. Size to Table 4-C for a 2027 permit — and plan checkers, stop red-lining clinic exam rooms at 4 ACH once the supplement is effective.

Two ways to comply

Table 4-C gives the designer a choice. You can hit the air-change option (the outdoor/total ACH columns), or use the Rp-Ra air-class option — a 62.1-style ventilation-rate calc. For a general exam room, that second path is 7.5 cfm per person plus 0.12 cfm per square foot, Air Class 1. Pick whichever sizes your system more efficiently.

The fine print that still bites

The lighter table comes with conditions worth reading before you draw:

• Nitrous oxide: a treatment room used for nitrous procedures must add anesthetic-waste-gas exhaust, and its minimum total air changes jump to 6 — and the Rp-Ra air-class option is off the table there.
• Toilet exhaust: not less than 70 cfm per water closet.
• Pressure differential: provide roughly a 10% supply-to-return/exhaust cfm differential, but not less than 25 cfm, regardless of room size.
• VAV minimum: for variable-air-volume zones, Vpz-min = 1.5 × Voz.

One more change rides in the same package, and it hits every OSHPD job, not just clinics: Section 407.3.1 now requires all Table 4-A balancing to be performed by a qualified independent agency certified by the AABC, NEBB, or TABB, in accordance with Section 403.10. Today that certified-third-party language lives only in Section 417.0, for isolation and protective-environment rooms. If it holds, budget and schedule a certified independent TAB agency on these projects.

What CrossBeam does with it

CrossBeam reads the mechanical schedule and room list, works out which clinic rooms route to Table 4-C versus hospital Table 4-A, and flags an exam room still sized to 4 air changes or a balancing scope that skips the certified-agency requirement. You get the right ventilation rate for the room — and the date it starts to apply — without cross-referencing three code sections by hand.