- AII rooms
- PE rooms
- Operating rooms (ORs), including delivery rooms (Caesarean)
- be designed so that all ductwork within the building is under negative pressure; Exception to 22.214.171.124(a): Ductwork located within mechanical equipment rooms. Positive-pressure exhaust ductwork located within mechanical equipment rooms shall be sealed in accordance with SMACNA duct leakage Seal Class A2.
- be located such that they reduce the potential for the recirculation of exhausted air back into the building.
- Exhaust discharge outlets from AII rooms, bronchoscopy and sputum collection exhaust, pharmacy hazardous-drug exhausted enclosures, and laboratory work area chemical fume hoods shall additionally be arranged to discharge to the atmosphere in a vertical direction (with no rain cap or other device to impede the vertical momentum) and at least 10 ft (3 m) above the adjoining roof level.
- Exhaust discharge outlets from laboratory work area chemical fume hoods shall discharge with a stack velocity of at least 2500 fpm (1180 L/s).
- Exhaust discharge outlets from AII rooms, bronchoscopy and sputum collection exhaust, and laboratory work area chemical fume hoods shall be located not less than 25 ft (8 m) horizontally from outdoor air intakes, openable windows/doors, and areas that are normally accessible to the public.
|Space Designation (According to Function)||Filter Bank No. 1 |
|Filter Bank No. 2 |
|Operating rooms (ORs); inpatient and ambulatory diagnostic and therapeutic radiology; inpatient delivery and recovery spaces||7||14|
|Inpatient care, treatment, and diagnosis, and those spaces providing direct service or clean supplies and clean processing (except as noted below); |
|Protective environment (PE) rooms||7||HEPAc,d|
|Laboratory work areas, procedure rooms, and associated semi-restricted spaces||13b||NR|
|Administrative; bulk storage; soiled holding spaces; food preparation spaces; and laundries||7||NR|
|All other outpatient spaces||7||NR|
|Resident care, treatment, and support areas in inpatient hospice facilities||13||NR|
|Resident care, treatment, and support areas in assisted living facilities||7||NR|
- Informative Note: The minimum efficiency reporting value (MERV) is based on the method of testing described in ANSI/ASHRAE Standard 52.2 (ASHRAE [2017a]).
- Additional prefilters may be used to reduce maintenance for filters with efficiencies higher than MERV 7.
- As an alternative, MERV-14 rated filters may be used in Filter Bank No. 2 if a tertiary terminal HEPA filter is provided for these spaces.
- Informative Note: High-efficiency particulate air (HEPA) filters are those filters that remove at least 99.97% of 0.3 micron-sized particles at the rated flow in accordance with the testing methods of IEST RP-CC001.6 (IEST ).
- Locate humidifiers within AHUs or ductwork to avoid moisture accumulation in downstream components, including filters and insulation.
- A humidity sensor shall be provided, located at a suitable distance downstream from the injection source.
- Controls shall be provided to limit duct humidity to a maximum value of 90% rh when the humidifier is operating.
- Duct takeoffs shall not be located within the humidifier's absorption distance.
- Humidifier control valves shall be designed so that they remain off whenever the AHU unit is not in operation.
- Humidifier water shall be treated with a reverse osmosis process, a UV-C sterilization light source, and a submicron filter. Informative Note: For more information, see ASTM (2011) in Appendix B.
- Treated humidifier water shall be continuously circulated from the source to the humidifier valves. All valves, headers, and piping not part of the recirculation loop shall drain completely when not in use.
- Ports suitable for testing water quality shall be provided in the treated humidifier water piping system.
- Moisture eliminators shall be provided as required to prevent moisture accumulation in ductwork.
- Surfaces of air distribution devices shall be suitable for cleaning. Supply air outlets in accordance with Table 6.7.2 shall be used.
- The supply diffusers in ORs shall be designed and installed to allow for internal cleaning.
- Psychiatric, seclusion, and holding patient rooms shall be designed with security diffusers, grilles, and registers.
|Space Designation (According to Function)||Supply Air Outlet Classificationa|
|Operating rooms (ORs)b, procedure rooms||Supply diffusers within the primary supply diffuser array: Group E, nonaspirating
Additional supply diffusers within the room: Group E
|Protective environment (PE) rooms||Group E, nonaspirating|
|Wound intensive care units (burn units)||Group E, nonaspirating|
|Trauma rooms (crisis or shock)||Group E, nonaspirating|
|AII rooms||Group A or Group E|
|Single-bed patient roomsc||Group A, Group D, or Group E|
|All other patient care spaces||Group A or Group E|
|All other spaces||No requirement|
- Informative Note: Refer to the 2017 ASHRAE Handbook-Fundamentals, Chapter 20 (ASHRAE [2017c]), for definitions related to outlet classification and performance.
- Surgeons may require alternate air distribution systems for some specialized surgeries. Such systems shall be considered acceptable if they meet or exceed the requirements of this standard.
Air distribution systems using Group D diffusers shall meet the following requirements:
- The system shall be designed according to "Design Guidelines" in System Performance Evaluation and Design Guidelines for Displacement Ventilation, Chapter 74.
- The supply diffuser shall be located where it cannot be permanently blocked (Informative Note: e.g., opposite the foot of the bed).
- The room return/exhaust grille shall be located in the ceiling, approximately above the head of the patient bed.
- The transfer grille to the toilet room shall be located above the occupied zone.
- Maintenance access shall be provided at all dampers.
- All damper locations shall be shown on design drawings.
- Air-handling systems shall be arranged such that damper activation will not damage ducts.
- An exterior vapor barrier shall be provided for insulation on cold surfaces. A vapor barrier is not required for insulation materials that do not absorb or transmit moisture.
- Existing insulation and duct lining accessible during a renovation project shall be inspected, repaired, and/or replaced as appropriate.
- Duct lining shall not be used in ductwork located down-stream of Filter Bank No. 2. Duct lining with an impervious cover may be allowed in terminal units, sound attenuators, and air distribution devices downstream of Filter Bank No. 2. This lining and cover shall be factory installed.
- Duct lining shall not be installed within 15 ft (4.57 m) downstream of humidifiers.