ASHRAE 170: Complete Guide to Ventilation of Health Care Facilities

ASHRAE Standard 170 establishes ventilation requirements for health care facilities to control airborne contaminants, reduce infection risk, and maintain appropriate environmental conditions for patients, staff, and visitors. This standard addresses ventilation rates, air quality, filtration, temperature, humidity, and pressure relationships. Understanding ASHRAE 170 is essential for healthcare facility designers, infection control professionals, and facility managers.

The standard provides specific requirements for various health care spaces, including patient rooms, operating rooms, isolation rooms, and support spaces. It integrates with ASHRAE 62.1 while establishing enhanced requirements for healthcare applications. This comprehensive guide covers all major sections, requirements, and practical applications.

Introduction to ASHRAE 170

Purpose and Scope

ASHRAE Standard 170 serves multiple critical functions:

Infection Control:

• Reduce airborne transmission
• Control contamination
• Protect patients
• Protect staff

Environmental Control:

• Maintain appropriate conditions
• Support healing
• Ensure comfort
• Protect equipment

Code Compliance:

• Health care facility codes
• Building codes
• Regulatory requirements
• Certification programs

Scope

Applies to:

• Hospitals
• Outpatient facilities
• Long-term care
• Ambulatory care
• All health care facilities

Ventilation Requirements

Ventilation Rates

Patient Rooms:

Ventilation Rate Calculation:

Where:

• $V_{total}$ = Total airflow (m³/h or cfm)
• $ACH$ = Air changes per hour
• $V_{room}$ = Room volume (m³ or ft³)

Outdoor Air Calculation:

Where:

• $V_{outdoor}$ = Outdoor airflow (L/s or cfm)
• $R_a$ = Outdoor air rate per area (L/s·m² or cfm/ft²)
• $A_{floor}$ = Floor area (m² or ft²)

Operating Rooms:

Support Spaces:

Ancillary Spaces:

Pressure Relationships

Pressure Requirements:

Pressure Differential Requirements:

Pressure Monitoring:

Pressure Calculation:

Where:

• $\Delta P$ = Pressure differential (Pa)
• $P_{supply}$ = Supply air pressure
• $P_{exhaust}$ = Exhaust air pressure

Airflow Balance:

For positive pressure:

For negative pressure:

Typical Airflow Differences:

Air Quality Requirements

Filtration

Filtration Requirements:

Filter Locations and Requirements:

Filtration Efficiency by Particle Size:

Filter Installation Requirements:

Outdoor Air Quality

Requirements:

• Meet ASHRAE 62.1 requirements
• Enhanced filtration if needed
• Monitoring
• Treatment if required

Outdoor Air Quality Standards:

Treatment Requirements:

If outdoor air exceeds limits:

Where:

• $E_{required}$ = Required removal efficiency
• $C_{limit}$ = Acceptable limit
• $C_{outdoor}$ = Outdoor concentration

Air Cleaning Systems:

Temperature and Humidity

Temperature Requirements

Space Temperature:

Temperature Control Requirements:

Humidity Requirements

Relative Humidity:

Humidity Control Requirements:

Dew Point Requirements:

Maximum dew point: 16°C (61°F) for most spaces

Where:

• $DP$ = Dew point (°C)
• $T$ = Temperature (°C)
• $RH$ = Relative humidity (%)

Humidification Requirements:

Dehumidification Requirements:

Special Requirements

Airborne Infection Isolation (AII)

Requirements:

• Negative pressure
• 12 ACH minimum
• MERV 14 filtration
• Exhaust to outdoors
• Anteroom recommended

AII Room Design:

AII Ventilation Calculation:

Where $V_{room}$ = Room volume (m³ or ft³)

Exhaust Requirements:

Protective Environment (PE)

Requirements:

• Positive pressure
• 12 ACH minimum
• HEPA filtration
• Supply from clean source
• Anteroom required

PE Room Design:

PE Ventilation Calculation:

HEPA Filtration Requirements:

Operating Rooms

Requirements:

• Positive pressure
• 20 ACH minimum
• Laminar flow (optional)
• MERV 14 filtration
• Temperature control

Operating Room Design:

Operating Room Ventilation:

Laminar Flow Systems:

Laminar Flow Benefits:

• Reduced airborne contamination
• Lower infection rates
• Improved air quality
• Enhanced surgical environment

System Design

Air Distribution

Design Requirements:

• Unidirectional flow (OR)
• Proper mixing (patient rooms)
• Avoid short-circuiting
• Proper exhaust location

Air Distribution Types:

Supply Air Distribution:

Exhaust Air Location:

Airflow Patterns:

Mixing Ventilation:

• Supply and return at ceiling
• Good mixing
• Uniform conditions
• Standard for most spaces

Unidirectional Flow:

• Supply from ceiling array
• Return at low level
• Laminar flow
• Operating rooms

Displacement Ventilation:

• Supply at floor
• Return at ceiling
• Natural convection
• Special applications

Controls

Control Requirements:

• Pressure monitoring
• Alarms
• Interlocks
• Status indication

Control Systems:

Alarm Requirements:

Interlock Requirements:

Redundancy

Requirements:

• Critical systems
• Backup systems
• Emergency power
• Reliability

Redundancy Requirements:

Emergency Power Requirements:

Reliability Requirements:

Additional Requirements

Air Change Rate Verification

Testing Requirements:

Airflow Measurement:

Where:

• $ACH$ = Air changes per hour
• $V_{measured}$ = Measured airflow (m³/min or cfm)
• $V_{room}$ = Room volume (m³ or ft³)

System Performance

Performance Metrics:

Performance Verification:

Practical Application Examples

Example 1: Operating Room

Room:

• Operating room: 50 m² (538 ft²)
• Height: 3 m (10 ft)
• Volume: 150 m³ (5,300 ft³)

Requirements:

• Outdoor air: 3.8 L/s·m²
• Total air: 20 ACH
• Positive pressure: +5 Pa
• MERV 14 filtration
• Temperature: 20-24°C

Calculations:

Outdoor air: $3.8 \times 50 = 190$ L/s (402 cfm)

Total air: $20 \times 150 = 3,000$ m³/h (1,767 cfm)

Supply air: 3,000 m³/h (1,767 cfm) Exhaust air: 2,850 m³/h (1,678 cfm) (maintains positive pressure)

System:

• Dedicated system
• MERV 14 final filter
• Pressure monitoring
• Temperature control

Example 2: Isolation Room (AII)

Room:

• Isolation room: 25 m² (269 ft²)
• Height: 3 m (10 ft)
• Volume: 75 m³ (2,650 ft³)

Requirements:

• Outdoor air: 2.4 L/s·m²
• Total air: 12 ACH
• Negative pressure: -5 Pa
• MERV 14 filtration
• Anteroom

Calculations:

Outdoor air: $2.4 \times 25 = 60$ L/s (127 cfm)

Total air: $12 \times 75 = 900$ m³/h (530 cfm)

Supply air: 800 m³/h (471 cfm) Exhaust air: 900 m³/h (530 cfm) (maintains negative pressure)

System:

• Dedicated exhaust
• MERV 14 exhaust filter
• Pressure monitoring
• Anteroom with pressure control

Example 3: Protective Environment (PE)

Room:

• PE room: 25 m² (269 ft²)
• Height: 3 m (10 ft)
• Volume: 75 m³ (2,650 ft³)

Requirements:

• Outdoor air: 2.4 L/s·m²
• Total air: 12 ACH
• Positive pressure: +5 Pa
• HEPA filtration
• Anteroom

Calculations:

Outdoor air: $2.4 \times 25 = 60$ L/s (127 cfm)

Total air: $12 \times 75 = 900$ m³/h (530 cfm)

Supply air: 900 m³/h (530 cfm) Exhaust air: 800 m³/h (471 cfm) (maintains positive pressure)

System:

• Dedicated supply
• HEPA final filter
• Pressure monitoring
• Anteroom with pressure control

Best Practices

Design Practices

System Design:

• Exceed minimum requirements
• Consider redundancy for critical spaces
• Plan for maintenance access
• Document all systems

Air Distribution:

• Proper diffuser selection
• Avoid short-circuiting
• Optimize airflow patterns
• Consider local requirements

Controls:

• Reliable control systems
• Continuous monitoring
• Alarm systems
• Status indication

Operation Practices

Regular Testing:

• Airflow verification
• Pressure testing
• Filter performance
• System efficiency

Performance Monitoring:

• Continuous monitoring
• Trend analysis
• Performance tracking
• Issue identification

Maintenance:

• Regular filter replacement
• System cleaning
• Equipment maintenance
• Performance verification

Documentation:

• Test reports
• Maintenance records
• Performance data
• Issue tracking

Compliance and Certification

Code Compliance

Requirements:

• Meet ASHRAE 170 requirements
• Building code compliance
• Health department approval
• Certification programs

Verification:

• Design review
• Construction inspection
• Performance testing
• Documentation review

Certification Programs

Programs:

• Joint Commission
• CMS (Centers for Medicare & Medicaid Services)
• State health departments
• Facility-specific requirements

Conclusion

ASHRAE Standard 170 provides comprehensive ventilation requirements for health care facilities. Key aspects include:

Ventilation Requirements:

• Ventilation rates by space type
• Outdoor air requirements
• Total air changes
• Air distribution

Air Quality:

• Filtration requirements
• Outdoor air quality
• Monitoring requirements
• Treatment systems

Environmental Control:

• Temperature requirements
• Humidity requirements
• Pressure relationships
• Control systems

Special Requirements:

• Isolation rooms (AII)
• Protective environments (PE)
• Operating rooms
• Critical care spaces

By understanding and applying ASHRAE 170, designers can create safe and effective health care environments that support infection control, protect patients and staff, and maintain appropriate environmental conditions for healing and care delivery.