4.11.4 REFRIGERATOR AND FREEZER APPLICATIONS
(a) Refrigerator and freezer refrigeration motors and controls shall be
on the emergency power system. Refer to HVAC Standard Detail 15900-5.
(b) For dietetic units product load is low because the product is
usually received infrequently, weekly or even monthly, and its
temperature is the same as the storage temperature. Lights are kept
off, except when a worker is inside the refrigerator or freezer, but
the unit coolers run continuously (except for defrost cycle for freezer
units).
(c) See paragraph 2.11.4 for the autopsy cold room ventilation.
(d) Unit coolers for freezers shall be equipped with electric defrost
and heated drain pan. All drains shall run through the wall or floor,
trapped outdoors, and discharge to an open site sanitary drain.
(e) Where multiple walk-in freezers are involved, consider providing a
central water-cooling system, possibly a closed circuit cooling tower
with a glycol-water loop to remove the heat. If not, water-cooled
condensing units with water regulating valves shall be used. Where a
condensing unit is located in a closet size room, mount the condensing
unit on the rack approximately four feet high to make the unit
accessible. Double tier racks may be provided for multiple condensing
units.
(f) If fan room or other mechanical space cannot be conveniently close
for locating compressor(s), a well-ventilated compressor room shall be
provided near the walk-in refrigerator/freezer. Units or mechanical
rooms shall not be located in interstitial space.
4.12
XENON GAS
4.12.1 GENERAL
The restricted areas of the Nuclear Medicine Department, namely,
Imaging Room (Patient Examination Room) and Storage & Preparation Area
(also known as Radiopharmacy Laboratory or Hot Laboratory) use Xenon
Gas (Xe - 133). Xenon Gas, being a radioactive material, requires
special ventilation considerations in accordance with the Nuclear
Regulatory Commission (NRC), publication `Guide for Preparation of
Applications for Medical Use Program', Guide 10.8, Appendix 0 dated
August, 1987 - Revision 2.
4.12.2 DESIGN CONSIDERATIONS
(a) The Imaging Room and Storage & Preparation Area should be kept
under negative pressure by exhausting at least 15 percent more air than
the supply air. The recirculation of air is not permitted from these
spaces.
(b) The Storage & Preparation Area is generally equipped with a
radioisotope fume type H3 hood. The exhaust requirements for H3 hood
are outlined in Article 2.11.
(c) The use of the Xenon gas depends upon the number of patients
examined per 40 hours-week. This number can range from one to fifteen
HVAC DESIGN MANUAL
4-5
HVAC REQUIREMENTS FOR UNOCCUPIED AREAS
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