Basic Documentation

Siemens Industry, Inc. Page 3 of 8
Document No. 149-978
VAV Laboratory Room Supply Air
VAV laboratory room supply air fulfills several functions:
 It provides makeup air for fume hood exhaust
and the miscellaneous room exhausts.
 It maintains adequate room ventilation
 It maintains the room ambient temperature and
humidity.
When a laboratory room has multiple fume hoods,
the amount of makeup air needed for the fume hoods
is often more than sufficient to maintain room
ventilation and the required room ambient conditions.
Thus, the maximum fume hood exhaust
4
of a
laboratory room is usually the determining factor
4. When multiple VAV fume hoods are present, a VAV diversity
(usage) factor is often used to establish a maximum fume
hood exhaust airflow rate that is somewhat less than the
theoretical maximum.
regarding the maximum amount of room supply air
that must be provided. Therefore, in laboratories with
VAV fume hoods the supply air turndown
requirements will quite often be close to the fume
hood turndown requirements of 5-to-1.
Table 1 gives examples of 24 different VAV chemical
laboratory ro
oms beginning with a single lab module
5
type laboratory room with one small fume hood and
progressing up to a triple sized lab modules with
multiple large fume hoods. This table is a convenient
reference for the airflow ranges likely to be needed
for such laboratory rooms. The turndown ratios
required for the supply makeup airflow are given in
the far right hand column. Detailed descriptions of
each of the table's columns appear on the following
page.
5. Research facilities are often comprised of single and double
laboratory module rooms since the modular approach has
been found to optimize laboratory usage.