PTP 3111 - Hospital Air Distribution Systems (PDF).pdf

Hospital Air Distribution Systems - PTP 3111
Presented by: Jordan Enns & Kris Geyson

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® Price Industries, Incorporated 2022

This webinar will explore the unique air distribution requirements and engineering
solutions for a variety of spaces within a hospital including patient rooms and
operating rooms with a focus on contamination control strategies and post-
pandemic design considerations.
Upon successful completion of this course, the learner will be able to:
• Explain the engineering methods of contamination control
• Appreciate the benefits or future-proof and pandemic-resilient hospital design
• Recognize opportunities for pandemic-resilient retrofit projects
Course Description
Hospital Air Distribution Systems

Agenda
1.Contamination Control
2.Post-Pandemic Design Considerations
3.Post-Pandemic Design Applications
–Supplemental Ventilation & Air Purification
–Pandemic-Ready Patient Rooms
–Isolation Operating Rooms
4.Questions

Contamination Control

Importance of Air Distribution Systems
Improvements to infection control practices including
ventilation can reduce the rates of infection and the
spread of pathogens
CDC Surgical Site Infection Study
• 16,000,000 operative procedures performed in
2010
• 1.9% rate of surgical site infections (SSI) from
2006-08
• SSIs are associated with a 3% mortality rate
Values taken from a study on Surgical Site Infections by the Center of Disease Control (CDC)

Building Code Requirements
• Facility Guidelines Institute (FGI)
–Guidelines for Design and Construction of Heathcare Facilities
–Adopted ASHRAE 170 for all HVAC
• American Society of Heating, Refrigeration, Air
Conditioning Engineers (ASHRAE)
–ASHRAE 170-2021 - Ventilation of Healthcare Facilities
–Widely adopted in North America for design of healthcare facilities
(new and renovation)

Airborne Contamination Sources
• Recirculated Supply Air
• Infiltration
• Patients/Staff

Control of airborne particulate levels may
be achieved by:
1) Reduction of source emissions
2) Removal/Inactivation of emissions with
filtration in the mechanical ventilation
system, UV-C, etc.
3) Capture of emissions at source with
localized equipment/exhaust, pressure
differential, etc.
4) Dilution of emissions with mechanical
ventilation & strategic airflow pathways

Filter Efficiency
ASHRAE Standard 52.2 - https://www.ashrae.org/File%20Library/Technical%20Resources/COVID-19/52_2_2017_COVID-19_20200401.pdf
ISO Standard 29463 - https://www.iso.org/standard/51837.html
Contamination Control – Removal
HEPA (High Efficiency Particulate Air Filter) – 99.97% efficient @0.3um
ULPA (Ultra Low Particulate Air Filter) – 99.9995% efficient @0.12um
Minimum
Efficiency
Reporting
Value
High
Efficiency
MERV 13 or greater
recommended by ASHRAE
for pathogen removal

Filter Construction
Cardboard/Plastic Frame Aluminum Frame w/Gasket Aluminum Frame w/Gel Seal
Contamination Control - Removal

Filtration Within an HVAC System
• Air handler
–Air intake (MERV 5 typical)
–Recirculated sections (MERV 8 typical)
• In duct
–In line in duct
–Part of fan terminal system
• Room-side/terminal diffuser
–HEPA is typical for critical areas

Ultraviolet Germicidal Irradiation (UVGI)
• UV-C: Ultraviolet light with a wavelength between 200-280 nanometers and is most
effective at 254 nanometers
• Intensity: The measurement used to quantify the level of UV-C exposure that is typically
measured in µW/cm2
• Dosage: Intensity x Exposure time, measured in µW-s/cm2
High Dosage required to “Inactivate on the Fly”
“The effectiveness of a UV-C system to inactivate microorganisms
in the air and/or on surfaces has been amply demonstrated”
– ASHRAE Position Document on Filtration and Air Cleaning, January 2018

Types of UVGI Disinfection Systems
• In-duct air decontamination
– Acts on air moving through ductwork
–Used with filtration to increase cleaning
• In-duct surface decontamination
–Acts on HVAC equipment surfaces
• Upper-room/upper-air decontamination
–Acts on room air in a safe disinfection zone
above occupants
• Portable room decontamination
–Acts on room surfaces
–Room must be unoccupied
https://www.ashrae.org/file%20library/technical%20resources/covid-19/ashrae-
filtration_disinfection-c19-guidance.pdf
Images
1. https://www.cmmonline.com/
articles/what-is-upper-room-uvgi
2. https://www.edisonairpurifiers.com
/commercial/
3. https://www.aquaductt.com/uv-
disinfection-mobile-room.html

Combining Filtration and UVGI
• Minimum filtration levels required by ASHRAE
–Physical removal of debris
–Particulate not affected by UVGI
–Filter performance and maintenance known and predictable
• UV combined with filtration to boost effectiveness
–In room purifiers combine HEPA filter and UV
–In duct UV with MERV system filtration

Air Changes Per Hour (ACH)
• The number of times the total
volume of air in a space is
completely removed and
replaced in one hour.
• Due to mixing and ventilation
effectiveness, 100% of room
air is not exchanged for each
air change
Contamination Control – Dilution
ACH =
𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆 𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴 𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅 𝑐𝑐𝑐𝑐𝑐𝑐 ∗60 (
𝑚𝑚𝑚𝑚𝑚𝑚
ℎ𝑟𝑟
)
𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴 𝑠𝑠𝑠𝑠.𝑓𝑓𝑓𝑓. ∗𝐻𝐻𝐻𝐻𝐻𝐻𝐻𝐻𝐻𝐻𝐻 (𝑓𝑓𝑓𝑓.)

Airflow Pathways - Standard Mixing
Used in most commercial HVAC
• Supply air mixes with room air to
maintain temperature and dilute
contaminants
• In healthcare this is typical in common
areas like corridors, cafeterias, waiting
rooms, etc.
• Specialised spaces with contamination
control requirements use other ventilation
techniques

Airflow Pathways - Strategic
• Move air from clean to less clean areas
• Wash essential areas with clean airflow
• Remove contaminated airflow before it is
mixed with room air
Airborne Infectious Isolation Room
Operating Room

Positive Pressure Differential
• Pressure inside is greater than outside
• Supply > Exhaust
• Air moves out of room
• Used to keep spaces clean
Negative Pressure Differential
• Pressure is lower inside than outside
• Exhaust > Supply
• Air moves into room
• Used to contain contaminants
Contamination Control – Capture
Examples
• Airborne Infectious
Isolation Room
• Hazardous Drug
Compounding Pharmacy
• Chemical Laboratories
Examples
• Operating Room
• Protective Environment
Room
• Burn Unit

Airflow Offset Control
• Maintains a constant CFM offset between
supply and exhaust valves (5%-20%)
• Independent of room pressure
• Most common solution
Pressure Control
• Airflow control setpoint based on room
pressure
• Less common approach
Note: a tightly sealed space is
necessary for pressurized applications
Airflow Offset Example
100 CFM supply
90 CFM exhaust
10% offset – positive pressure

Anteroom
• Transition area between the
corridor and the room of concern
• Used for contamination control,
staging, and gowning
• Pressurized relative to both
corridor and patient room
reduces probability of
contaminants flowing in and out
of room

Relative Humidity
0%
High Humidity:
- Condensation
- Fungal Growth
- Bacterial Growth
- Moisture Damage
- Odors
- Increased Health Risks
100%
40%
Low Humidity:
- Dry nose
- Dry eyes
- Longer airborne virus
travel time
60%
Ideal

Post-Pandemic Design Considerations

The pandemic created huge strain on the healthcare system, and impacted
patients seeking care of other conditions. Future hospital design should allow a
hospital to maintain essential operations.
The “Pandemic Resilient Hospital” report from ASHE, ARUP, HKS, and the
American Hospital Association defines 7 principles for Pandemic-Resilient Design
https://www.ashe.org/pandemic-resilient-hospital

Versatile
In addition to meeting pandemic needs, the design must work for everyday use
and non-infectious patient care to be financially viable.
Consider:
• Flex spaces that can be converted to screening and triage areas
• Spaces that can be easily converted to accommodate contagious patients
– Convert to negative room pressure
• Design for both airborne and surface contact contagions
https://www.hfmmagazine.com/articles/4329-designing-the-post-pandemic-hospital

Surge Ready
The design needs to support an increase in the number of patients and patient
severity on the existing footprint.
Consider:
• Larger patient rooms that can accommodate
– More equipment to suit patients through their entire stay
– Multiple patients
• Spaces that can safely accommodate additional patients

Clean Air & Surfaces
Design to reduce the transmission of infectious particles, while supporting
ease of maintenance and cleaning of air and surfaces.
Consider:
• Increasing outside ventilation air or system filtration levels
• Implementing in-room air purifiers
• Touch-free surfaces (doors, sinks, etc. )
• Readily available PPE

Isolate, Contain & Separate
Facilitate the separation of infectious patient care to keep the rest of the
patient and staff population safe and support continuity of operations.
Consider:
• Telemedicine – estimated that 25% of outpatient services could move to
telemedicine
• Remote waiting areas – intake information done from patients vehicle
(when possible)
• Emergency department screening areas – vestibules, designated
symptomatic waiting areas
https://www.bloomberg.com/news/articles/2021-02-23/how-the-pandemic-is-transforming-hospital-design

Isolate, Contain & Separate
Facilitate the separation of infectious patient care to keep the rest of the
patient and staff population safe and support continuity of operations.
Consider:
• Designated Pandemic units - separate wards or facilities for pandemic
patients.
– Permits access to routine health concerns amid pandemic
– Ambulatory care facilities more accessible for patients
– Fewer facilities require pandemic resilient upgrades
https://www.bloomberg.com/news/articles/2021-02-23/how-the-pandemic-is-transforming-hospital-design

Flow
The design supports clear channels for circulation and flow to support safe
movement and minimize transmission risk.
Consider:
• Single pass flow – separate entry and exit points, one-way foot traffic
• Designated PPE donning and doffing areas
• Reduced intra-hospital travel
– Telemedice reduces overall traffic
– Fewer stops per patient visit - sign in, waiting room, exam room, lab, etc.

Key HVAC Considerations
• Ventilation & Air Change Rate
– Maximize outside air
– Dilute contaminants
• Air Treatment
– Remove or capture contaminants
• Pressure Control
• Airflow Pattern
– Move air from clean to less clean
https://www.ashe.org/pandemic-resilient-hospital

Supplemental Ventilation & Air Purification

Supplemental Air Purification
Methods for Improving Indoor Air Quality
• Ventilate with outdoor air
–Consider weather, pollution, and
capabilities of existing HVAC system
• Increase system filter efficiency
–Consider capabilities of existing HVAC
system
• Supplement with in-room air purifier
https://schools.forhealth.org/wp-content/uploads/sites/19/2020/06/Harvard-Healthy-Buildings-
Program-Schools-For-Health-Reopening-Covid19-June2020.pdf

Puraflo Fan Filter Units
use cleanroom
technology to deliver
HEPA-filtered airflow
and an increased air
change rate with no
impact on the existing
HVAC system,
effectively reducing
exposure to airborne
contaminants.

Reverse Flow Construction
Allows selection of the discharge
diffuser to optimize thermal comfort
and air distribution in the space.
Dual-Outlet Reverse Flow Construction
Ideal for applications like dental offices and
patient rooms where a negative room
pressure as well as an increased air change
rate is desired.

How to Size an Air Purifier
Example: Personal Care Home
Room Size: 200 ft2
Ceiling Height: 9 ft.
Room Volume: 1,800 ft3
Additional ACH: 6
Flow Rate: 180 cfm
Sound: 25 NC
Equipment:
• 1x Puraflo Exhaust (24 in. x 48 in.)
• 1x Supply Diffuser

How to Position an Air Purifier
• Move air from clean to less-clean areas
• Avoid interference with physical obstacles &
existing air distribution
• Avoid short circuiting airflow
• In-ceiling options preserve floor space

Pandemic-Ready Patient Rooms

Purpose
• Pandemics create a sudden
increase in demand for Negative
Pressure Isolation Rooms
• Hospitals typically build with few
AIIR as they are infrequently
used and more expensive to
operate than standard patient
rooms

Concept
• Build one room that can be used for
standard patient care or converted to
a negative pressure isolation room
• Change from Normal Operation of a
patient room to Isolation Mode at the
touch of a button
• Fast conversion eliminates the need
for time consuming and unsightly
field modifications
Staff should have the ability to convert regular patient rooms—
or even a whole unit, if needed—into an isolation zone
-Tim Eastwood, Stantec

ASHRAE Standard 170-2021 Ventilation of Health Care Facilities dictates the
following requirements for standard patient rooms and airborne infectious
isolation rooms

The Price Critical Area
Recirculation/Exhaust System
(CARES) manages airflow for a
patient room as part of a
pandemic-ready solution
• Combines an exhaust flow fan filter
unit and a flush face radial flow
diffuser
• Cleanroom-grade construction and
HEPA Gel Seal prevent filter bypass
• Room-side replaceable HEPA filter
and MERV8 pre-filter

Normal Operation
CARES
Normal Operation: Fresh air
supplied to room.
Return
Normal Operation: Damper
open to allow return airflow
to the AHU.
Exhaust
Normal Operation: Damper closed.
Pressure Monitor
Normal Operation: No room pressure
requirement
Supply
Fresh air supplied to room.
Supply – 90 cfm (4 ACH)
Return – 90 cfm

Isolation Mode
CARES
Isolation Mode: HEPA filtered air is exhausted
to maintain room pressure while fresh supply air
and the remainder of the filtered air is
recirculated to the space.
Return
Isolation Mode: Damper closed.
Exhaust
Isolation Mode: Damper open to allow exhaust
airflow and negative room pressure.
Pressure Monitor
Isolation Mode: Measures and displays room.
pressure. Actives FFU, closes return damper, and
modulates exhaust damper to maintain negative
room pressure.
Supply – 90 cfm (4 ACH)
Recirculated – 180 cfm (8 ACH)
Exhaust – 100 cfm
Supply
Fresh air supplied to room.

Other considerations
• Keep patients in one place for
entire cycle of care
• Larger rooms to accommodate
various types of equipment
• Ability to move multiple patients
into the same room
• Windows to corridor so staff can
monitor patients without entering
• Anterooms for donning/doffing PPE

Isolation Operating Rooms

ASHRAE Standard 170-2021 Ventilation of Health Care Facilities dictates
the following requirements for operating rooms
• Laminar diffuser array with at least 70% coverage concentrated above
that surgical zone, with airflow velocity of 25-35 CFM/ft2
• 20 ACH total (4 min. ACH outdoor air)
• Minimum 2 (4 recommended) low-level returns
• Positive pressure, min 0.01” w.c.
• 20-60% RH

• Operating rooms are designed with
positive room pressure to manage
infection control.
• Airborne Infectious Isolation
Rooms are designed with negative
room pressure to contain
pathogens
For surgery on a contagious
patient an isolation OR is required
Cleveland Clinic’s Lutheran Hospital | Cleveland, OH

A Negative Pressure Anteroom can maintain pressure relationships
https://karpinskieng.com/insights/healthcare-building-codes-and-design-after-covid-19
https://www.hfmmagazine.com/articles/3867-infection-control-during-construction
• Temporary anteroom
–Modular walls, set us as
necessary
–Necessary HVAC (supply
diffuser, exhaust fan) built
in place
–Or use portable HEPA unit

Summary
• Methods of contamination control
–Removal, dilution and capture of contaminants
through filtration, increased ventilation rates,
airflow pathways, and pressure control
• Pandemic-resilient hospital design
–Regard for versatility, surge capacity, clean air and
surfaces, isolation and containment, and flow
• Opportunities for pandemic-resilient retrofits
–Supplemental ventilation and air purification,
pandemic-ready patient rooms, isolation operating
rooms

• ASHRAE Standard 52.2 Method of Testing General Ventilation Air Cleaning Devices for Removal Efficiency by Particle Size -
https://www.ashrae.org/File%20Library/Technical%20Resources/COVID-19/52_2_2017_COVID-19_20200401.pdf
• ISO 29463 High-Efficiency Filters and Filter Media for Removing Particles in Air - https://www.iso.org/standard/51837.html
• EN 1822 European Standard High Efficiency Air Filters (EPA, HEPA and ULPA) - https://www.en-standard.eu/din-en-1822-1-high-efficiency-air-
filters-epa-hepa-and-ulpa-part-1-classification-performance-testing-marking/
• ASHRAE Standard 170 Ventilation of Health Care Facilities - https://www.techstreet.com/ashrae/standards/ashrae-170-
2017?product_id=1999079&ashrae_auth_token=12ce7b1d-2e2e-472b-b689-8065208f2e36
• ASHE, Pandemic Resilient Hospital Report - https://www.ashe.org/pandemic-resilient-hospital
• Bloomberg, What the Post-Pandemic Hospital Might Look Like - https://www.bloomberg.com/news/articles/2021-02-23/how-the-pandemic-is-
transforming-hospital-design
• Karpinski Engineering, Healthcare Building Codes and Design After COVID-19 - https://karpinskieng.com/insights/healthcare-building-codes-and-
design-after-covid-19
• HFM Magazine, Designing the Post-Pandemic Hospital - https://www.hfmmagazine.com/articles/4329-designing-the-post-pandemic-hospital
• Stantec, Pandemic Preparedness: How Hospitals can Adapt Buildings to Address Worst-Case Scenarios -
https://www.stantec.com/en/ideas/topic/covid-19/pandemic-preparedness-how-hospitals-can-adapt-buildings-to-address-worst-case-scenarios
• Harvard TH Chan School of Public Health, Schools for Health - https://schools.forhealth.org/wp-content/uploads/sites/19/2020/06/Harvard-Healthy-
Buildings-Program-Schools-For-Health-Reopening-Covid19-June2020.pdf
• SmithGroup, Healthcare Design Strategries for a Post-Covid World - https://www.smithgroup.com/sites/default/files/2021-
04/Healthcare%20Design%20Strategies%20for%20a%20Post-COVID%20World_SmithGroup%202021_Web.pdf
References

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