infection control - isolation rooms · o ashrae standard 170 “supply diffusers shall be above the...

HVAC Design for HealthcareInfection Control - Isolation Rooms

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HVAC Systems in HospitalsAn Effective HVAC System Controls Risk from Hospital-Acquired InfectionsHospital, clinics and other medicalfacilities pose several unique challenges thataren't present in traditional HVAC situations.As such, it's important for designers,engineers, installers, maintenance personneland other HVAC professionals to be familiarwith installing HVAC systems for medicalpurposes.

Not only can simple comfort be on the line,but patients can be put at risk by HVACsystems that don't function properly. Here is abrief introduction to HVAC systems formedical facilities and How you can go aboutdesigning a Isolation Room Within a HealthCare Facility.

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PLACE IMAGE HERE

Hospital-acquired infections (HAIs, also referred to as nosocomial infections) have a significantimpact on patient care. Mortality rates from HAIs are significant and affect the overall cost of health caredelivery. In the United States, HAIs occur in an estimated 4% to 5% of admitted patients; at an estimatedannual cost approaching $7 billion. It is generally agreed that 80 to 90% of HAIs are transmitted by directcontact, with 10% to 20% resulting from airborne transmission (representing 0.4% to 1% of admittedpatients) (Memarzadeh 2011a).

1.Contact, both direct and indirect, is the most common mode of transmission in health carefacilities and other indoor environments. HVAC has little impact on this mode of transmission.

2.Droplet transmission is characterized by dispersion of microorganisms from an infectedperson over short ranges (3–6 feet). The aerodynamics of this results in microbes contained in fluidsthat fall out of the air in rapid fashion.

3.Airborne transmission involves dissemination of microbes via droplet nuclei beyond shortranges, such as via an HVAC system.

HVAC systems can affect the distribution patterns of airborne particles bydiluting or concentrating them, moving them into or out of the breathingzones of susceptible persons, or by accelerating or decelerating the rateof growth of airborne microbes. Improperly operated and maintainedHVAC systems can even become a reservoir for microorganisms.

ROLE OF HVAC SYSTEMS IN INFECTION CONTROL3

Let us Understand Hvac Design for Healthcare Facility

HVAC design for health care facilities is all about providing a safer environment for patientsand staff. The basic difference between air conditioning for healthcare facility and that of otherbuilding types stem from:

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AIR MOVEMENTThe need to restrict air movement in and between the various departments (no cross movement).

DILUTIONThe specific requirements for ventilation and filtration to dilute and reduce contamination in the form of odor, airborne micro organisms and viruses, and hazardous chemical and radioactive substances. Ventilation effectiveness is very important to maintain appropriate indoor air quality.

PATIENT COMFORTThe different temperature and humidity requirements for various areas and the accurate control of environmental conditions.

DESIGN PARAMETERSThe design sophistication to minimize the risk of transmission of airborne pathogens and preserve a sterile and healing environment for patients and staff.

HOSPITAL ISOLATION ROOM HVAC SYSTEMDESIGN PRINCIPLES

ISOLATION ROOM

If your doctor wants you to be keptaway, or isolated, from other patientswhile you receive medical care, youmay be in a special hospital room,called an isolation room, to keep youseparate from other people.

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TYPES OF ISOLATION ROOMS

TYPES OF ISOLATION ROOMS

CODES/STANDARDSREFERANCESGUIDELINES

DESIGN CRITERIA DESIGN CONSIDERATION

EXAMPLE

Codes/ Standards/ References

“Guidelines for Environmental Infection Control in Health-Care Facilities”, Recommendations of CDC (centers for Disease Control & Prevention )and the Healthcare Infection Control Practices Advisory Committee (HICPAC), 2014

Codes:

International Mechanical Code (IMC)

Standard:

ANSI/ASHRAE/ASHE Standard 170 – Ventilation of Health Care Facilities (2017)

NFPA 101

Guidelines:

Facility Guidelines Institute (FGI) Guidelines (2014) – for ventilation refers to ASHRAE Standard 170 - 2017

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TYPES OF ISOLATION ROOMS3

Airborne infectious isolation (AII)

Protective environment (PE)

Combined AII/PE

Contact isolation

TYPES OF ISOLATION ROOMS3

Airborne infectious isolation (AII)

• These rooms are for patients having an airborne communicable disease

• In this type of infection, patient is the source of infection

• The ventilation system functions as one of multi-levels of infection control system

• The purpose is to contain patient-generated infectious microbial within the room, to prevent the spread of infection to other patients and staff.

What is a Airborne Infection Isolation (AII) Room

DESIGN CONSIDERATIONS FOR AN AII ROOM

HVAC COMPONENTS

• AIR TERMINALS

• FILTERATION SYSTEM

• EXHAUST SYSTEM

• MOINTERING DEVICE

• ANTE ROOM REQUIREMENTS

AIR TERMINAL TYPE TO BE USED IN AII ROOM

• FOR AII ROOM THETERMINAL TYPE ISCEILING DIFFUSEROF GROUP A & EFOR SUPPLY AND ARETURN DIFFUSEROR GRILL OFGROUP A OR E.

GROUP A TYPE OF DIFFUSER

FIL

• FOR AN AII ROOMASHRAE STANDARDREQUIRES THE AHU TOBE INSTALLED WITH TWOFILTER BANKS, ONEMERV 7 UP STEAM ANDTHE OTHER MERV 14 INTHE DOWN STREAM.

• FRESH AIR SHOULD BETAKEN IN FROM AHEIGHT OF 2 MTS ABOVEGROUND LEVEL ANDABOUT 10 MTS AWAYFROM ANY EXHAUST.

FILTERATION SYTEM WITHIN

AHU

Minimum Efficiency Reporting Value

PLUME / STACK EXHAUST• ALL AIR WILL BE

EXHAUSTED FROM AN AII ROOM BY VERTICAL EXHAUST

• ROOM EXHAUST MUST BE ON EMERGENCY POWER FOR AII ROOM

• AIR SHOULD BE DISCHARGED AT A HEIGHT OF 3MTS ABOVE ROOF LEVEL @ ≥ 2500 FPM.

ANTEROOM : ANTE ROOMS ARE RECOMMENDED FOR AII ROOM AND PE ROOM BUT NOT MANDATORY.

FOR COMBINATION ROOM

MONITERING DEVICE• AII rooms shall have a permanently installed

device and/or mechanism to constantly monitor the differential air pressure :--between the room (when occupied by patients with a suspected airborne infectious disease) and –the corridor, adjacent spaces of the room whether or not there is an anteroom

–A local visual means shall be provided to indicate whenever negative differential pressure is not maintained.

• A minimum of 0.01” of wg or 2.5 pa should be achieved.

DESIGN PARAMETERSFOR AN AII ROOM

SOURCE ASHRAE STANDARD 170

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Calculate ACH based on exhaust flowIf not occupied pressure relationship is maintained and min ACH 6Switching controls for reversible airflow (pressure relationship) shall 

not be permitted(note t)

Considering a room with dimensions : Length : 10 ftWidth : 10 ftAnd height : 10 ftVolume of the room will become :10*10*10 = 1000ft3

FORMULA FOR ROOM AIR CHANGES PER HOUR (ACH)

ACH = (60*CFM)/VOLUME

CFM = (ACH * VOLUME)/60

WE HAVE MIN ACH : 12 as per ashrae standard 170.

CFM = (12*1000)/60

=200 CFM

AII ROOM WITHOUT ANTE ROOM TOTAL EXHAUST 250 CFM

AII ROOM WITH ANTE ROOM

Volume of the room will become :10*10*10 = 1000ft3

FORMULA FOR ROOM AIR CHANGES PER HOUR (ACH)

ACH = (60*CFM)/VOLUME

CFM = (ACH * VOLUME)/60

WE HAVE MIN ACH : 12 as per ashrae standard 170.

CFM = (12*1000)/60

=200 CFM

AIR CHANGES IN ANTE ROOM .CONSIDERING TOILET AND ANTE ROOM

VOLUME TO BE 240 FT3MIN ACH FOR ANTE ROOM : 10 ACH

CFM = (10*240)/60= 40 CFM

200 CFM

50 CFM

300 CFM

50 CFM

TOTAL EXHAUST 350 CFM

TYPES OF ISOLATION ROOMS3

Protective environment (PE) ROOM

These rooms are meant for patients with weakened immune system

These patients need protection against infectious airborne agents

In this case it is the patient who must be protected from infectious microbials

Also protection from opportunistic organisms that are not a threat to healthy individuals

What is a PROTECTIVE ENVIRONMENT Room

DESIGN CONSIDERATIONS FOR AN PE ROOM

HVAC COMPONENTS

• AIR TERMINALS

• FILTERATION SYSTEM

• MOINTERING DEVICE

• ANTE ROOM REQUIREMENTS

AIR TERMINAL TYPE TO BE USED IN PE ROOM

• FOR AII ROOM THETERMINAL TYPE ISCEILING DIFFUSEROF GROUP E,NONASPIRATINGFOR SUPPLY AND ARETURN DIFFUSER.

FIL

• FOR AN PE ROOMASHRAE STANDARDREQUIRES THE AHU TOBE INSTALLED WITHFILTER BANK, ONE MERV7 UP STEAM AND THEOTHER HEPA AT THETERMINAL

• FRESH AIR SHOULD BETAKEN IN FROM AHEIGHT OF 2 MTS ABOVEGROUND LEVEL ANDABOUT 10 MTS AWAYFROM ANY EXHAUST.

FILTERATION SYTEM AHU AND AT THE SUPPLY

TERMINAL

Minimum Efficiency Reporting Value

ANTEROOM : ANTE ROOMS ARE RECOMMENDED FOR AII ROOM AND PE ROOM BUT NOT MANDATORY.

FOR COMBINATION ROOM

MONITERING DEVICE• AII rooms shall have a permanently installed

device and/or mechanism to constantly monitor the differential air pressure :--between the room (when occupied by patients with a suspected airborne infectious disease) and –the corridor, adjacent spaces of the room whether or not there is an anteroom

–A local visual means shall be provided to indicate whenever negative differential pressure is not maintained

• A minimum of 0.01” of wg or 2.5 pa should be achieved.

DESIGN PARAMETERSFOR AN PE ROOM

SOURCE ASHRAE STANDARD 170

Protective Isolation RoomRoom Supply and Exhaust Design Considerations

� Same requirements as AII room except:o Location of supply diffusers and exhaust grilles

� ASHRAE Standard 170 “Supply diffusers shall be abovethe patient bed… Diffuser design shall limit air velocity at

patient bed to reduce patient discomfort� ASHRAE Standard 170 “Return/exhaust grilled shall be

locate near the patient door.”o SA must be from AHU that has code‐required filtration:� Min MERV 7 prefilters and HEPA final filters (ASHRAE) or

� MERV 14 final filters with terminal HEPA filter

TYPES OF ISOLATION ROOMS3

Combined AII/PE rooms are for patients suffering from a weakened immune system who also have an airborne communicable disease. In this type of room, HVAC issues involve a combination of both AII room and PE room considerations.

Combined AII/PE Rooms•These rooms are for patients suffering from a weakened immune system and also having an air-borne communicable disease•The ventilation issues involved is combination of both AII and PE room

Combination Airborne InfectiousIsolation/Protective Environment Rooms

� PE requirements govern supply diffuser and exhaustgrille locations:

o ASHRAE Standard 170 “Supply diffusers shall be above thepatient bed.

o ASHRAE Standard 170 “Return/exhaust grilled shall belocate near the patient door.”

� Two permanently installed monitoring devices are requiredo One between the AII/PE room and the ante room

o One between the ante room and the corridor

Combination Airborne InfectiousIsolation/Protective Environment Rooms

� For immune suppressed patients with a airborne infectious disease� CDC and ASHRAE 170 allow two options: positive or negative ante room

TYPES OF ISOLATION ROOMS3

Contact isolation rooms are for patients having a communicable disease that is not airborne.

Contact Isolation•The patients who are put in these rooms are not having communicable disease that is airborne•Example of such cases are:–Diarrhoea–Draining wound–Body lice and so on

Supply system:

•SA from PE to maintain 12 ach: 1,400 cfm•SA to ante room: 250 cfm•Constant volume box to maintain total SA / Total SA = 1,400 cfm + 250 cfm = 1,650 cfm•Reheat coil to provide space temperature control

Transfer air from PE room to ante room and ante room to corridor

•Assume mid range in tightness – use 300 cfm transfer air (TA)

Return/Exhaust system:

•Air from ante room and PE room may be returned to AHU / RA from Ante Room: 250 cfm•Toilet exhaust must be exhausted to outside / TE: 100 cfm•PE room RA = PE room SA – TA to ante room – TA to toilet = 1,400 cfm - 300 cfm - 100 cfm = 1,000 cfm•Constant volume box to maintain total RA •Total RA = RA from PE room + RA from ante room = 1,000 cfm + 250 cfm = 1,250 cfm

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