ASHRAE Standard 170 Ventilation for Health Care Facilities

Criteria for ASHRAE 170 compliance focuses on HVAC requirements for medical environments. Ventilation criteria addressed in ASHRAE 170 includes the need for an emergency power supply for continual ventilation, parameters for temperature and humidity ranges, air filtration, and air dispersal/removal locations.

While HVAC requirements designated by NFPA 99 mostly deal with the necessity to exhaust air from anesthetizing areas continually, ASHRAE 170 also specifically addresses building pressure, air filtration, and infection control. Imaging rooms that house anesthetic gases must also meet the same stringent air change rate requirements as operating rooms.

Building Pressure

Building pressure directly affects temperature, humidity, and airflow. HVAC systems must be designed and implemented in such a way as to ensure compliance with both NFPA 99 and ASHRAE 170 requirements. This requires deep level thought during the earliest design stages to arrive at viable solutions. 

The pressure between specific areas or rooms must also be considered, with positive and negative pressures assigned based on the risk of infectious air being transmitted to “clean” areas or rooms. Much of the design requirements will be determined based on the governing body’s assessment of “risk” in any given setting. 

Air Filtration

Healthcare facilities require extra filtration compared to many other types of environments. The need to filter out contaminants, including respiratory droplets like those associated with coronavirus transmission, often necessitates the installation of HEPA filters. It’s recommended that air from rooms with a high risk of contaminants be exhausted outside whenever possible rather than recirculated. 

Recirculated air must pass through the recommended filter before being reintroduced. It should only be fed into the original room or rooms with a less “clean” rating than the room of origin. 

Infection Control

Infectious disease spread through the air of a healthcare facility is typically accomplished by the dissemination of particles trapped in respiratory droplets and expelled into the air by talking, coughing, or sneezing. HVAC design as pertains to air filtration and air exhaust must be tightly controlled to prevent the spread of infection. Surface cleaning must also be rigorously implemented.

The design of medical spaces and facilities can offer many design challenges for both HVAC designers and facility owners. Ideally, healthcare facilities will exceed minimum requirements as laid out by NFPA 99, ASHRAE 170, and associate codes and manuals. HVAC system designers, engineers, installers, and maintenance personnel will then support the integrity of such systems to maintain ongoing compliance.

If you’re interested in learning how to implement NFPA 99 into your medical space design, the design team specialists at Therma are here to help.