6.5 ASHRAE 170 Ventilation/Air Pressure & Legionella Water Management Plans

6.5 ASHRAE 170 Ventilation & Legionella Water Management Plans

Healthcare infection prevention relies heavily on the physical plant's aerodynamic and hydrologic infrastructure. Airborne transmission of respiratory pathogens and waterborne proliferation of opportunistic premise plumbing pathogens represent profound clinical threats to vulnerable patients. Environmental Services leaders must collaborate closely with Facilities Management and Infection Prevention to enforce ANSI/ASHRAE/ASHE Standard 170 (Ventilation of Health Care Facilities) and execute comprehensive Legionella Water Management Plans mandated by CMS and The Joint Commission.

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1. ANSI/ASHRAE/ASHE Standard 170: Healthcare Ventilation

Standard 170, developed jointly by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) and the American Society for Health Care Engineering (ASHE), is incorporated into the Facility Guidelines Institute (FGI) Guidelines and enforced by CMS and TJC (EC.02.05.01).

+-----------------------------------------------------------------------------+
|                   PRINCIPLES OF HEALTHCARE AIR PRESSURE DYNAMICS            |
|                                                                             |
|   [ POSITIVE PRESSURE ROOM (+) ]          [ NEGATIVE PRESSURE ROOM (-) ]    |
|   Objective: Keep Pathogens OUT           Objective: Keep Pathogens IN      |
|                                                                             |
|        Supply CFM > Exhaust CFM                Exhaust CFM > Supply CFM     |
|                                                                             |
|             +----------+                            +----------+            |
|             | Clean    |                            | Corrid.  |            |
|             | Air In   |                            | Air In   |            |
|             v          v                            v          v            |
|          [ PROTECTED ROOM ]                      [ CONTAMINATED ROOM ]      |
|             |          |                            |          |            |
|             +----+-----+                            +----+-----+            |
|                  |                                       |                  |
|                  v (Air Flows OUT)                       v (Air Flows IN)   |
|           [ Corridor / Anteroom ]                 [ Dedicated Exhaust / HEPA]|
|                                                                             |
|   - Pressure: ≥ +0.01 in w.g. (+2.5 Pa)   - Pressure: ≤ -0.01 in w.g. (-2.5Pa)|
|   - Application: ORs, PE Rooms, Clean Lin. - Application: AIIR, Soiled Util,  |
|     Sterile Core, Pharmacy Cleanrooms.      EVS Closets, Waste Holding.     |
+-----------------------------------------------------------------------------+

Directional Airflow & Pressure Differentials

Directional airflow is established by creating a calibrated volumetric imbalance between supply airflow and exhaust/return airflow:

• Minimum Pressure Differential: Standard 170 requires a minimum pressure differential of ±0.01 inches water gauge (±2.5 Pascals) across the closed doorway between the controlled room and adjacent spaces.
• Air Changes per Hour (ACH): Represents the number of times the total volume of air in a room is completely replaced in one hour ($ACH = \frac{\text{Airflow in CFM} \times 60}{\text{Room Volume in } ft^3}$).

ASHRAE 170 Room Pressure & Ventilation Parameters

[!WARNING] Read the row label, not the room's nickname. Standard 170's Table 7-1 values above are the current ANSI/ASHRAE/ASHE Standard 170-2021 figures as incorporated into the FGI Guidelines, and four of them are routinely misquoted:

• Clean linen storage is 2 total ach, not 4. The 4-ach figure belongs to clean workroom or clean holding, a different Table 7-1 row. Both are positive to adjacent spaces, which is the point EVS is actually accountable for.
• Soiled workroom, soiled holding, and the decontamination room are 6 total ach with 2 outdoor ach. The older 10-ach figure was the pre-2021 value; it is not an "existing facility" allowance, because Standard 170 governs new construction and renovation rather than grandfathered space.
• Soiled linen sorting and storage is a separate row at 10 ach — do not merge it with soiled utility. This is the row that governs the soiled-linen holding space in your own department.
• The 12-ach AIIR figure is Standard 170's single value. The familiar "6 ach for existing rooms" is CDC's 2005 TB guideline for facilities built before the current standard, not an ASHRAE row.

Patient rooms carry a 4-ach minimum with no required pressure relationship; the 6-ach number applies only to single-bed patient rooms using Group D diffusers, calculated on the volume from the floor to 6 ft above it.

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2. EVS Operational Protocols in Controlled Air Environments

EVS technicians working in specialized ventilation zones must adhere to rigorous procedural controls to avoid compromising the aerodynamic pressure barrier:

+-----------------------------------------------------------------------------+
|                 EVS AIR PRESSURE VERIFICATION & ENTRY PROTOCOL              |
|                                                                             |
|   1. PRE-ENTRY PRESSURE VERIFICATION                                        |
|      - Visually inspect digital magnehelic gauge or ball-in-tube indicator. |
|      - Verify indicator confirms correct differential (Green light / in-spec)|
|      - If digital monitor is in ALARM: STOP, do not enter; notify nurse &   |
|        Facilities immediately.                                              |
|                |                                                            |
|                v                                                            |
|   2. ANTEROOM / DOOR DISCIPLINE                                             |
|      - Never open the corridor door and patient room door simultaneously.   |
|      - Allow anteroom doors to fully close and latch before proceeding.     |
|      - Ensure room door remains tightly closed during entire cleaning cycle.|
|                |                                                            |
|                v                                                            |
|   3. AIRBORNE REMOVAL WASHOUT TIME (DISCHARGE)                              |
|      - For AIIR rooms vacated by TB, Measles, or Varicella patients:        |
|      - Verify required ACH washout time (CDC Table B.1) has elapsed before  |
|        entering without respiratory protection:                             |
|        * At 12 ACH: 99.9% airborne removal requires 35 minutes.             |
|        * At 6 ACH:  99.9% airborne removal requires 69 minutes.             |
+-----------------------------------------------------------------------------+

• Physical Smoke Tube / Flutter Strip Verification: In facilities lacking digital continuous pressure monitors, EVS and nursing verify negative airflow using a chemical smoke tube or lightweight flutter strip held at the base of the closed door (smoke or strip must be drawn inward toward the room).
• High-Efficiency Particulate Air (HEPA) Filtration: Mobile HEPA air scrubbers deployed during ICRA construction or temporary isolation must be certified at 99.97% efficiency at 0.3 micrometers and exhausted directly outdoors where feasible.

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3. CDC / CMS / TJC Legionella Water Management Plans

Waterborne pathogens in healthcare premise plumbing present a major hazard to immunocompromised patients. In 2017, CMS issued Survey & Certification Memo S&C 17-30, mandating that all certified hospitals, critical access hospitals, and long-term care facilities develop and maintain comprehensive Water Management Plans (WMPs) compliant with ASHRAE Standard 188 (Legionellosis: Risk Management for Building Water Systems). The Joint Commission enforces this under EC.02.05.01 EP 14.

+-----------------------------------------------------------------------------+
|                  LEGIONELLA PNEUMOPHILA ECOLOGY & TRANSMISSION              |
|                                                                             |
|   [ MICROBIOLOGICAL PROFILE ]                                               |
|   - Gram-negative, flagellated aquatic bacillus.                            |
|   - Colonizes biofilms, pipe scale, sediment, and protozoan amoebae.        |
|                                                                             |
|   [ OPTIMAL TEMPERATURE GROWTH PROFILE ]                                    |
|   - < 68°F (20°C): Dormant (Survives but does not multiply).                |
|   - 77°F - 113°F (25°C - 45°C): OPTIMAL GROWTH RANGE (High Risk).           |
|   - 120°F - 140°F (49°C - 60°C): Survival range; reproduction ceases.       |
|   - > 140°F (60°C): Rapid microbial death (Pasteurization).                 |
|                                                                             |
|   [ TRANSMISSION VECTOR ]                                                   |
|   - Inhalation of aerosolized water droplets (1-5 µm) into pulmonary alveoli|
|   - Micro-aspiration of contaminated drinking water or ice.                 |
|   - NEVER TRANSMITTED PERSON-TO-PERSON.                                     |
|   - Causes Legionnaires' Disease (severe pneumonia) and Pontiac Fever.      |
+-----------------------------------------------------------------------------+

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4. EVS Operational Execution in Water Safety Programs

While Facilities Management oversees municipal water inlets, hot water boiler loops, and secondary biocidal injection systems (chlorine dioxide, copper-silver ionization), the Environmental Services Department is directly responsible for terminal premise plumbing hygiene and point-of-use fixtures.

+---------------------------------------------------------------------------------------------------+
|                         EVS WATER MANAGEMENT & HYGIENE RESPONSIBILITIES                           |
|                                                                                                   |
|  WATER RESERVOIR / FIXTURE  HAZARD MECHANISM                 MANDATORY EVS PROTOCOL & CADENCE     |
|  -------------------------  -------------------------------  ------------------------------------ |
|  Clinical Ice Machines      Biofilm & mold in ice storage    Monthly / Quarterly deep clean and   |
|                             bins, chutes, and evaporator.    sanitization; external scoop holster;|
|                                                              no food/beverage storage in ice bin. |
|  Sink Faucets & Aerators    Biofilm buildup & mineral scale  Routine cleaning & descaling; replace|
|                             harboring Pseudomonas & Legion.  clogged aerators; wipe spouts.       |
|  Clinical Sink P-Traps      Stagnant water reservoir for     Clean basin clean-to-dirty; avoid    |
|                             CRE, Pseudomonas, Legionella.    high-pressure spraying into drain.   |
|  Vacant Room Fixtures       Water stagnation in dead legs    Weekly flushing of all taps, showers,|
|  (Low-Occupancy Units)      causes biocidal dissipation.     and commodes for 3-5 minutes.        |
|  Eyewash Stations           Stagnant microbial reservoir.    Weekly 15-minute flush verification. |
|  Toilet Bowls / Commodes    Aerosolization during flushing.  Close lid before flush; apply foam   |
|                                                              bowl cleaner along sides gently.     |
+---------------------------------------------------------------------------------------------------+

Clinical Ice Machine Decontamination Protocol

Ice machines in patient care units are high-risk environmental reservoirs. Contaminated ice machines have been implicated in multiple fatal nosocomial outbreaks of Legionella, Pseudomonas, and Mycobacterium:

1. Routine Inspection & Sanitization: EVS must clean and sanitize the exterior housing, dispenser chute, and drain pan daily.
2. Deep Internal Descaling & Disinfection: Executed on a strict monthly or quarterly schedule using EPA-registered ice machine sanitizers and food-grade descaling acids to remove calcium scale.
3. Sanitary Scoop Protocol: The ice scoop must be stored in a dedicated, clean, external wall-mounted holster. The scoop must never be left resting inside the ice bin. The ice bin must never be used to chill bottled drinks, medications, or biological specimens.

Stagnant Plumbing Line Flushing Protocol

In low-census units, renovated wings, or unoccupied patient rooms, stagnant water sitting in supply pipes rapidly loses its municipal residual chlorine or monochloramine disinfectant. Biofilms proliferate rapidly in these "dead legs." EVS standard operating procedures must enforce systematic weekly flushing:

• Run hot and cold sink faucets at full flow for 3 to 5 minutes.
• Run showerheads for 3 to 5 minutes into the drain.
• Flush all commodes and urinals repeatedly to pull fresh treated water from the main distribution loop through all terminal fixtures.