MIL-HDBK-1191
Ductwork for laboratory equipment is covered elsewhere in this section.
8.11.5.2
Return Air Plenums. Corridors shall not be used as return air
plenums in any portions of facilities. Exceptions allowing transfer air
for toilets and janitor's closets, as provided in NFPA 90A and 101,
(references 8d and 8h) shall be permitted. Utilization of above-ceiling
areas as return air plenums shall not be permitted in inpatient or
critical-care areas of facilities. Utilization of above-ceiling areas for
return or exhaust air in portions of facilities not classified as
healthcare occupancy is discouraged but may be considered on an individual
project basis when justified by overriding cost or vertical space
constraints.
8.11.5.3
Duct lining. The utilization of duct lining materials is
generally discouraged in all medical facilities. These materials may
harbor dust and moisture, providing an ideal environment for the
propagation of pathogenic or noxious microorganisms. In addition,
inevitable duct modifications or careless installation procedures lead to
breaks in the duct lining sealer. Factory fabricated sound attenuators,
packed type, which comply with ASTM C1071 and UL 181, shall be used in lieu
of duct lining to attenuate fan noise, when practicable. Duct lining,
where permitted, shall also meet the requirements of ASTM C1071 and UL 181.
No duct lining materials which are porous to the airstream may be utilized
in any air distribution system serving inpatient diagnostic, treatment, or
bedroom areas (including all Critical spaces); factory fabricated sound
attenuators with liners which resist moisture penetration of the acoustical
packing material may be utilized for these applications.
8.12
Maintenance Provisions.
8.12.1
General Personnel Access. Safe and practical means of
personnel access must be provided to, and within, all areas of the facility
where equipment is located, to adequately provide for operation,
maintenance, and replacement (O&M) of the equipment. Access to equipment
rooms from outside the facility should be provided where feasible. Within
equipment rooms, a minimum of 0.75M (2.5 ft) (of clearance is generally
required at all service points to mechanical equipment to allow adequate
personnel access and working space. The design of O&M personnel accessways
should not provide less than 1.7M (5.5 ft) of overhead clearance (except on
intermittent basis), or require personnel to climb over equipment or crawl
on hands and knees. When rooftop air handling units are provided,
coordinate with the architectural designer to provide pavers or other
personnel access pathways which will not damage the roof.
8.12.2
Equipment Clearances. Minimum clearances between electrical
and mechanical equipment shall be as required by NFPA 70, (reference 8m).
Assure that practical means are provided for the removal/replacement of the
largest and/or heaviest equipment item(s) located in the facility. Provide
adequate pull space for all coils, heat exchangers, chillers, boiler tubes,
and filters. Sufficient space shall be provided in above-ceiling areas to
facilitate equipment installation and O&M. For building designs utilizing
interstitial floor distribution zones, further guidance is provided at
Section 19.
8-15
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