ARCHITECTURAL AND ENGINEERING DESIGN REQUIREMENT
LEGEND and NOTES
Relative Humidity (1 characters). This is the
relative humidity to be maintained in a space as
part of the designed conditions.
RH may vary from 30-60%.
RH must be controlled at 55%, + or - 5%.
Filtration (5 characters) indicates the level and
location of filtration required. See HVAC Note B.
Intermediate filtration in percent (2 characters).
Final filtration in percent (2 characters).
Exhaust Outside (1 character). This column
lists areas that require 100% exhaust directly
to the outside.
Exhaust to outside required.
Exhaust not required.
See HVAC Notes (3 characters)
among individual facilities, depending upon functional requirements.
Designers shall coordinate with the Using Service for each facility
to determine whether disease isolation (negative pressurization) or
"switchability" (room convertible from disease isolation to
protective isolation, or vice versa) is discouraged, facility
function and program limitations may dictate that this feature be
General Filtration. Prefilters, 25%, are required for all outdoor
air. The values for the 25%, 80% and 90% filters are by the
atmospheric dust spot efficiency test. The atmospheric dust spot
efficiencies are the minimum average and are based on ASHRAE Standard
52-76. Designation "99" indicates that a 99.97 % efficiency HEPA
filter is required, based on the DOP (Dy-Octyl Phthalate, or bis 2-
ethylhexylphthalate) test method. The DOP test efficiency is based
on MIL-STD 282. All filters should be installed to prevent leakage
between the filter segments and between the filter and its supporting
During period of non-use, the air volume may be reduced to 6 air
changes per hour, while maintaining the required air balance. 90
percent intermediate filtration is indicated because the same AHU
normally serves adjacent OR/DR support areas requiring this level of
filtration. Where the AHU serves only OR/DR spaces, the 90%
intermediate filter may be replaced with a 60%-80% filter, intended
to prolong the life of the final filter.
When the Using Service intends the routine usage of nitrous oxide in