FGI AII Room Requirements: Design and Ventilation (2010 Edition)

Below –0.01 in. wc against adjacent spaces, an AII room is not held negative to them. Airborne infection isolation (AII) rooms hold contagious patients, stop infectious air at the door, and the 2010 edition requires 12 total air changes per hour (ASHRAE/ASHE 170-2008 Table 7-1, reprinted as Part 6 of the FGI 2010 Guidelines). This article states the FGI 2010 Guidelines and ANSI/ASHRAE/ASHE Standard 170-2008 section by section. It does not state the 2026 edition; see the edition section below before you design to any number here.

Which FGI edition applies to your project?

Every number in this article comes from the 2010 FGI Guidelines for Design and Construction of Health Care Facilities and the ASHRAE/ASHE 170-2008 text printed in it. That is not the current edition. The FGI 2026 edition has been released (fgicodes.org shows “2026 Edition is Here!” and renames the documents “FGI Codes for Planning and Design” and “FGI Handbooks for Planning and Design”). States adopt FGI editions on their own schedules, so a project may be governed by the 2014, 2018, 2022 or 2026 edition, or by an older one. The edition’s AII table, section numbers and exception wording can differ. Ask the authority having jurisdiction (AHJ), usually the state health department, which edition and which ASHRAE 170 version it has adopted, and design to that text.

What are airborne infection isolation (AII) room requirements?

An AII room is used for isolating the airborne spread of infectious diseases such as measles, varicella and tuberculosis (FGI 2010 §2.1-8.2.2.1; ASHRAE 170-2008 Table 7-1 note u). FGI 2010 §2.2-2.2.4.2(1) requires at least one AII room in a general hospital, and the number of additional AII rooms for individual nursing units is increased based on an Infection Control Risk Assessment (ICRA). Under §2.1-2.4.2.2(1) each AII room has only one bed. AII rooms are located within individual nursing units or grouped as a separate isolation nursing unit, and §2.1-2.4.2.1(3) permits normal acute care use when isolation is not needed. When used for routine care, differential pressure requirements remain unchanged (§2.1-8.2.2.1(1)). Later editions changed the ventilation rate for that case: ASHRAE interpretation IC 170-2021-3 (approved February 1, 2022; ashrae.org) says that in ANSI/ASHRAE/ASHE 170-2021, when an AII room is not used for airborne infection isolation, all room air must still be exhausted directly outdoors, but total air changes can drop from 12 to 4 as long as the negative pressure relationship to adjacent areas is unchanged.

What are the HVAC requirements for an AII room?

The ventilation numbers come from ANSI/ASHRAE/ASHE Standard 170-2008, which FGI 2010 includes as Part 6.

Table 7-1 note u adds that the room design must allow normal patient care when isolation is not needed, and that supplemental recirculating HEPA devices may be used to increase equivalent air changes, but the outdoor air changes are still required. Per §7.2.1: the room carries a permanently installed device that constantly monitors differential pressure and a local visual indicator of lost negative pressure (a); all air is exhausted directly outdoors (b); exhaust from the AII room, its anteroom and its toilet room is discharged outdoors without mixing with any non-AII exhaust (c); exhaust grilles or registers are directly above the patient bed or on the wall near the head of the bed unless that is shown not to be practical (d); and the room envelope is sealed to limit leakage at 0.01 in. wc (2.5 Pa) differential pressure (e). Note u also says HEPA-filtered exhaust from AII rooms may mix with non-AII exhaust before discharge, which reads against §7.2.1(c); ask the AHJ how it reads the pair.

What architectural details does an AII room require?

FGI 2010 §2.1-2.4.2.4(1) sets three architectural details: perimeter walls, ceiling and floor, including penetrations, are sealed tightly so air does not infiltrate from outside or other spaces (a); all room exit doors have self-closing devices (b); and doors have edge seals (c). For window treatments (§2.1-2.4.2.4(2)), use smooth-surfaced, easy-to-clean, wipeable, nonpleated treatments; fabric drapes and curtains are not used as window treatments, while washable fabric privacy curtains are permitted. AII rooms and their anterooms have seamless flooring with integral coved base (§2.1-7.2.3.2(13)). AII rooms are semirestricted areas, so ceilings are smooth, scrubbable, nonabsorptive and nonperforated (§2.1-7.2.3.4(2)(a)). If a lay-in ceiling is used it is gasketed, or each tile weighs at least one pound per square foot; perforated, tegular, serrated-cut or highly textured tiles are not acceptable (§2.1-7.2.3.4(2)(b)).

What support spaces are required with an AII room?

Under FGI 2010 §2.1-2.4.2.2 each AII room also complies with the medical/surgical patient room requirements (§2.2-2.2.2) and has: a hand-washing station in the patient room (a second station outside the entrance is permitted, (2)); an area for gowning and storage of clean and soiled materials directly outside or inside the entry door (3); and a separate room with a toilet, bathtub (or shower) and hand-washing station for each AII room (4). AII rooms in the NICU must comply with §2.1-2.4.2 except the separate toilet, bathtub or shower (§2.2-2.10.4.2(2)).

Is an anteroom required in an AII room?

No. FGI 2010 §2.1-2.4.2.3 says an anteroom is not required; if one is part of the design concept it provides space to don personal protective equipment and all its doors have self-closing devices. When an anteroom is provided, airflow is from the corridor into the anteroom and from the anteroom into the patient room (§2.1-8.2.2.1(3)). Each AII room has a permanently installed visual mechanism that monitors the pressure differential between the AII room and the corridor, whether or not an anteroom is present (§2.1-8.2.2.1(2)). A combination AII/PE room is different: it must have an anteroom (§2.2-2.2.4.5(3)).

What is a combination AII/PE room?

A combination airborne infection isolation and protective environment (AII/PE) room is for profoundly immunosuppressed patients with prolonged neutropenia (for example allogeneic or autologous bone marrow or stem cell transplant patients) who require a protective environment and have an airborne infectious disease (FGI 2010 §2.2-2.2.4.5). Hospitals with PE rooms include at least one. Requirements in 2010:

• The room meets the PE room requirements plus the combination-room rules, and has an anteroom with space to don PPE and self-closing doors (§2.2-2.2.4.5(2)-(3)).
• Supply air complies with the PE requirement: HEPA filters just before the room, and before the anteroom if one is provided (§2.2-8.2.2.3(1), referring to §2.2-8.2.2.2(2)).
• Exhaust from the room and anteroom complies with the AII room requirements (§2.2-8.2.2.3(2)).
• The anteroom airflow pattern is either from the anteroom to both the patient room and the corridor, or from both into the anteroom (§2.2-8.2.2.3(3)).
• Rooms with reversible airflow to switch between PE and AII functions are not permitted (§2.2-8.2.2.3(4); Table 7-1 notes t and u).
• Two permanently installed visual pressure monitors: patient room to anteroom, and anteroom to corridor (§2.2-8.2.2.3(5)).
• Ventilation: positive pressure, 2 outdoor and 12 total air changes, all air exhausted outdoors, and a minimum differential pressure of 0.01 in. wc (FGI 2010 Table 2.1-2 and its note 2).

What are the retrofit rules for AII rooms?

ASHRAE 170-2008 §7.2.1(b) has one exception: an AII room retrofitted from a standard patient room, where exhausting directly outdoors is impractical, may be ventilated with recirculated air from the room’s exhaust provided the air first passes through a HEPA (MERV 17) filter. Do not use this for new construction. Check whether your state’s adopted edition keeps the exception.

Key numbers at a glance (FGI 2010 / ASHRAE 170-2008)

Common mistakes to avoid

1. Mixing AII exhaust with building exhaust. Under ASHRAE 170-2008 §7.2.1(c), exhaust from the AII room, anteroom and toilet room is discharged outdoors without mixing with non-AII exhaust.
2. Assuming an anteroom removes the pressure monitoring requirement. Under FGI 2010 §2.1-8.2.2.1(2) the monitor measures the AII room against the corridor whether or not an anteroom is present.
3. Turning off the pressure control between isolation patients. Under §2.1-8.2.2.1(1), differential pressure requirements remain unchanged when the room serves routine care.
4. Specifying reversible airflow for combination AII/PE rooms. Not permitted (§2.2-8.2.2.3(4)).
5. Applying the retrofit exception to new construction. It applies to rooms retrofitted from standard patient rooms where direct exhaust is impractical (§7.2.1(b)).
6. Using lay-in tile without checking weight or gaskets. Each tile must weigh at least 1 lb/sf or the ceiling must be gasketed (§2.1-7.2.3.4(2)(b)); check the product data sheet.
7. One pressure monitor on a combination AII/PE room. Two are required (§2.2-8.2.2.3(5)).
8. Designing to 2010 numbers without checking adoption. Confirm the AHJ’s adopted FGI edition and ASHRAE 170 version first.