Ashrae Journal - October 2008 - 55

Operating Rooms In Class B and C operating rooms, the airflow needs to be unidirectional, downwards, and the average velocity of the diffusers shall be 25 to 35 cfm/ft2 (127 L/s · m2 to 178 L/s · m2). (Average velocity is specified as cfm/ft2 so it is clear that the critical parameter is the average airflow velocity that is measured at the face of the supply diffuser.) The diffusers need to be concentrated to provide an airflow pattern over the patient and surgical team. This aligns with the results of research that studied particulate concentration as a function of air-distribution patterns and air exchange rates for operating rooms.3 A minimum positive pressure differential of 0.01 in. w.c. (+2.5 Pa) with respect to all adjoining spaces is required. Reserve Cooling Sources that MERV 7 filters are more readily available and the filtration efficiency is equally satisfactory. Radiant Cooling and Heating Systems Although radiant panels have been used in health care applications for some time, application guidance had not been previously addressed (neither in the Guidelines nor Chapter 7, Health Care Facilities, of the ASHRAE Handbook. Minimum criteria are provided in this standard. The dew-point criteria are intended to control the agglomeration of condensation. The minimum criteria are: 6.5.2 Radiant Cooling Systems If radiant cooling panels are utilized, the chilled water temperature shall always remain above the dew-point temperature of the space. 6.5.3 Radiant Heating Systems If radiant heating is provided for an airborne infection isolation room, a protective environment room, a wound intensive care unit (burn unit), or a room for any class of surgery, either flat and smooth radiant ceiling panels with exposed cleanable surfaces or radiant floor heating shall be used. Isolation Rooms Reserve capacity is required for certain large cooling systems with some exceptions. The standard states that “The number and arrangement of cooling sources and related essential accessories shall be sufficient to support the owner’s facility operation plan upon breakdown or routine maintenance of any one of the cooling sources.” Reserve capacity is required by this standard if 1) the total central cooling plant capacity is greater than 400 ton (1407 kW); and 2) the building is located in geographic parts of the country where the 1% cooling dry-bulb temperature is more than 85°F (29°C) (2005 ASHRAE Handbook— Fundamentals). Considerable latitude is afforded by the owner’s facility operation plan, e.g., the plan can allow for specific duration of time that the facility can operate without cooling, the plan can allow load shedding to maintain service to critical spaces, etc. Filters The standard provides some clarifying guidance for the airborne infection isolation room. The exhaust from the room should include the exhaust from the toilet and the anteroom (where provided). The location of the exhaust grille is specified to be in the vicinity of the head of the bed in alignment with CDC guidelines.4 The allowable air leakage can be quantified during the design because of the differential pressure control requirement, i.e., 0.01 in. w.c. (2.5 Pa). The Standard’s guidance for airborne infection isolation rooms: c) All exhaust air from the Airborne Infection Isolation (AII) rooms, associated anterooms and associated toilet rooms shall be discharged The standard specifies a minor difference from the recommendations in the Guidelines. The first filter banks are indicated to be MERV 7 filters in the standard. The Guidelines recommend a MERV 8 filter. Investigation by the ASHRAE project committee concluded October 2008 www.info.hotims.com/16018-5 ASHRAE Journal 55

Ashrae Journal - October 2008

Table of Contents for the Digital Edition of Ashrae Journal - October 2008

Ashrae Journal - October 2008

Contents

Commentary
Industry News
Letters
ASHRAE HQ Dedication Booklet
ASHRAE Rebuilds HQ to Reflect Mission
Feature Articles
ASHRAE's Living Lab
Meetings and Shows
Sizing Pipe Using Life-Cycle Costs
Feature Articles
Energy-Efficient Data Centers: A Close-Coupled Row Solution
The Future of 90.1
Ventilation Standard for Health Care Facilities
Grosvenor Humidity Chart
ASHRAE Research Report
ASHRAE Honor Roll
Building Sciences
Special Products
Emerging Technologies
Product Showplace
Classified Advertisting
Advertising Index
Ashrae Journal - October 2008 - Ashrae Journal - October 2008
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Contents