Welcome to Part VI of our ongoing series breaking down ASHRAE standards and their impact on modern commercial HVAC design, energy efficiency, and indoor environmental quality (IEQ).
For healthcare facilities like hospitals, clinics and nursing homes, indoor air quality (IAQ) is critical to infection control and patient healing. To provide a safe environment for patients and staff, ASHRAE Standard 170 offers ventilation guidelines for mechanical engineering teams and facility managers when designing healthcare HVAC systems.
In this installment of our ASHRAE Standards series, we’ll learn about Standard 170 for healthcare facilities and how ERVs can help with meeting this standard.
What Is ASHRAE Standard 170?
Developed in partnership with the American Society of Health Care Engineering (ASHE) and the Facility Guidelines Institute (FGI), ASHRAE Standard 170 establishes minimum ventilation requirements for healthcare facilities. First published in 2008, the primary objective of Standard 170 is to mitigate healthcare-associated infections (HAIs) by controlling airborne pathogens, chemical vapors, bioaerosols, and environmental parameters like temperature and humidity.
In addition to infection mitigation, Standard 170 provides prescriptive ventilation design requirements for achieving environmental control. This includes room pressure relationships, air changes per hour (ACH), energy efficiency options, filtration minimums, and odor control.
Which Facilities Are Covered by ASHRAE Standard 170?
ASHRAE Standard 170 builds on top of ASHRAE Standard 62.1, which provides ventilation guidelines for commercial and multi-family buildings. Healthcare facilities will apply one or the other standard, depending on function of the space. Standard 62.1 provides guidelines for non-clinical healthcare zones such as administrative offices, lobbies, breakrooms, and cafeterias. Standard 170 is applied when the space requires clinical care, patient isolation, or sterilization.
The following are examples of healthcare spaces covered under Standard 170:
- Hospitals & Acute Care: Inpatient spaces, surgical suites, intensive care units (ICUs), emergency departments, operating rooms (ORs), and airborne infection isolation rooms (AIIRs).
- Outpatient & Ambulatory Care: Day-surgery clinics, outpatient procedure rooms, urgent care centers, and renal dialysis centers.
- Specialized Clinical Spaces: Compounding pharmacies (cleanrooms), sterile processing departments (SPD), and clinical laboratories.
- Residential & Long-Term Care: Nursing homes, hospice facilities, and assisted living centers with dedicated clinical or skilled nursing spaces.
- Veterinary & Animal Care Facilities (Adapted Application): While not explicitly mandated by human healthcare codes, veterinary surgery suites, animal isolation wards, and research labs routinely adopt Standard 170 guidelines as the gold standard for contamination and odor control.
In addition, some spaces have prescribed ventilation rates in both Standard 62.1 and 170. In these cases, facilities should use the higher of the two air change rates.
What Are Key Design Considerations for ASHRAE Standard 170?
Achieving full compliance with ASHRAE Standard 170 requires strict adherence across mechanical design, space layout, and continuous monitoring. To satisfy regulatory mandates and protect patient safety, engineering and facility teams must factor in multiple design considerations:
ASHRAE Standard 170 – Key Design Considerations |
|
|---|---|
| Directional Airflow & Pressure Control | Certain rooms must have positive pressure differentials to ensure air moves outward from high-risk areas or negative pressure to trap hazardous airborne contaminants within a room. |
| Direct Exhaust Requirements | Air drawn from high-hazard zones (e.g., AIIRs, soiled utility, and pharmacy compounding) must be exhausted directly outdoors with zero recirculation back into general building HVAC systems. |
| Air Change Rates (ACH) | Total air changes per hour and fresh outdoor air exchange rates help to dilute airborne contaminants. These can range up to 20 ACH and 4 outdoor ACH minimum for high-risk areas such as operating rooms. |
| Energy Efficiency | Facilities can utilize energy recovery systems to reduce their energy demands, however these systems cannot allow for any cross-contamination of exhaust air back to the supply airstream. Certain rooms are also able to reduce their air change rates if unoccupied. |
| Filtration Systems | Rooms can range from MERV-8 filters for catching dust and mold spores up to MERV-16 and HEPA filters for capturing bacteria, viruses and respiratory droplets. |
| Tight Humidity Limits | Relative humidity must generally be maintained within tight pa-rameters (typically 20% to 60%, varying by clinical zone). High humidity encourages mold and bacterial growth, while excessively dry air increases viral transmission rates and generates static charge risks near delicate surgical equipment. |
| Air Quality Monitoring & Controls | Critical spaces require continuous air quality monitoring to catch when room pressure, temperature or humidity are outside the specified range. Demand controlled ventilation and building automation systems can help maintain healthy IAQ through sensors and programmed controls. |
The Energy Challenge: High Air Changes Means High Operating Costs
To satisfy Standard 170’s many ventilation requirements, healthcare facilities need a powerful HVAC system that provides frequent 100% outdoor air changes. This can lead to high operating costs since conditioning raw outdoor air typically requires massive amounts of energy to heat, cool, humidify, or dehumidify it to precise indoor setpoints.
In addition, healthcare facilities must move high volumes of air to maintain pressure relationships. Pushing air through dense filtration systems creates significant static pressure resistance, requiring large air handling units.
Conditioning high volumes of outdoor air and maintaining room pressure differentials makes HVAC systems one of the largest single utility expenses for hospitals, clinics, and nursing homes.
The System Solution: Decoupling Ventilation with DOAS and Static-Plate ERVs
To keep operating costs under control while maintaining ASHRAE ventilation standards, healthcare facilities can utilize several energy efficient solutions. These options include decoupling ventilation systems, recovering energy to condition incoming air, and reducing ventilation to unoccupied spaces.
Dedicated Outdoor Air Systems (DOAS):
A DOAS unit uses dedicated equipment to handle 100% of the outdoor air brought indoors for ventilation, delivering it directly to occupied spaces or in conjunction with local terminal equipment. By separating ventilation from space temperature control, outdoor air undergoes filtration and thermal conditioning with high-efficiency energy recovery before being distributed through independent ductwork. This decoupled architecture allows each system to operate in its optimal design envelope with each function working in dedicated silos.
Energy Recovery Ventilators (ERVs):
ERVs help facilities lower energy loads by capturing heat and humidity from outgoing room air and transferring it to incoming outdoor air. ASHRAE Standard 170 permits energy recovery between exhaust air and incoming outdoor air, provided the equipment prevents cross-contamination. ERVs with a static-plate core keep airstreams separate, allowing healthcare facilities to increase ventilation, lower their heating and cooling costs, all without risk of cross-contamination.
Demand Controlled Ventilation (DCV):
Standard 170 allows airflow modulation and setback controls primarily through unoccupied turndown. When spaces like patient rooms, operating rooms, and lab work areas are unoccupied, ventilation rates can be reduced. This process can be automated through occupancy sensors or BMS scheduling systems.
High-Efficiency Variable Frequency Drives (VFDs):
Equipping supply, return, and exhaust fans with VFDs allows continuous adjustment of fan speed to match dynamic system static pressure needs, reducing fan energy consumption exponentially under partial load conditions.
Achieve ASHRAE Standard 170 with Energy Efficiency
Achieving the stringent ventilation and infection control mandates of ASHRAE Standard 170 does not have to come at the cost of high utility bills. By integrating DOAS and ERV units into HVAC systems, healthcare facilities can continuously deliver high-volume outdoor air changes while reducing ventilation energy loads.
Frequently Asked Questions (FAQs)
Is ASHRAE Standard 170 mandatory by law?
ASHRAE Standard 170 is legally enforced through adoption by state health departments, local building codes, and federal agencies. Notably, the Centers for Medicare & Medicaid Services (CMS) and The Joint Commission (TJC) enforce compliance with the Facility Guidelines Institute (FGI) Guidelines, which formally incorporate ASHRAE Standard 170 as their normative HVAC standard.
Is energy recovery allowed in healthcare HVAC systems?
Energy recovery is allowed in healthcare HVAC systems if cross-contamination is prevented. Standard 170 permits energy recovery ventilators (ERVs) and energy recovery wheels between general exhaust and outdoor air intake streams provided the equipment prevents cross-contamination. For hazardous exhaust streams (like AIIR or chemical exhaust), run-around coil loops are typically required because they completely separate the fluid loops and eliminate any possibility of air carryover.
Does ASHRAE Standard 170 cover all areas in healthcare facilities?
ASHRAE Standard 170 applies specifically to clinical spaces, patient care, and supportive medical rooms where airborne infection control, environmental parameters, or contamination risks directly impact patient and staff safety. Rooms that have non-clinical functions should follow ASHRAE Standard 62.1, the indoor air quality guidelines for commercial and institutional buildings.
ASHRAE 170 is considered a specialized standard that builds on the foundation of ASHRAE 62.1. When areas with prescribed rates in both Standard 62.1 and 170 exist, the higher of the two air change rates shall be used.
Example non-clinical spaces covered by ASHRAE 62.1:
- Administrative offices
- Standard waiting rooms and lobbies
- Staff breakrooms, cafeterias, and dining areas
- Gift shops and public retail spaces
- Mechanical rooms, IT closets, and storage rooms
What are recent changes in the 2025 edition of ASHRAE Standard 170?
The 2025 edition of ASHRAE Standard 170 introduces several significant updates, technical refinements, and spatial expansions compared to the 2021 edition.
Combined System Sizing (Standard 170 + Standard 62.1): The calculation for total outdoor air at the systems level was overhauled. For AHUs serving both Standard 170 (clinical) and Standard 62.1 (non-clinical) spaces, non-clinical spaces are calculated using 62.1 procedures, and the Standard 170 outdoor air volumes are summed directly into the system total.
Outpatient Unoccupied Turndown: Expanded and clarified allowable unoccupied turndown provisions specifically for outpatient and ambulatory care facilities, enabling greater energy savings when clinical spaces are closed.
Outdoor Air Delivery & Discharge Geometries: Clarified minimum separation distances between exhaust/relief outlets and outdoor air intakes, along with updated discharge stack height requirements for complex roof configurations (e.g., proximity to parapets, sloped roofs, and maintenance access paths).
Construction Phase Ventilation: Reorganized and updated Section 10 to provide clearer guidelines for maintaining indoor air quality and pressure control during healthcare facility renovations and active construction phases.
Behavioral Health Additions: Expands space-specific functions to cover specialized behavioral health spaces (e.g., dedicated patient bedrooms, seclusion rooms, and resident rooms).