Demister Guidelines

DOE-STD-1066-99

14.8.2

Demister Guidelines

14.8.2.1

Where automatic deluge spray systems are installed in filter plenum

enclosures that do not contain prefilters, metal demisters should be

installed downstream of the automatic deluge spray sprinkler heads and

upstream of the first series HEPA filter.

14.8.2.2

Demisters should have a nearly 100 weight (wt) percent efficiency for

water drops 50 microns and larger. They should have an efficiency

greater than 99 wt percent for 1 to 50 microns with air flow velocities of

500 to 600 feet (153 to 183 meters) per minute,or at operating air flow

velocities with operating water flow deluge spray delivery rate.

14.8.2.3

Demisters should be located as far away as possible from the HEPA filters

(a minimum of 36 inches [91 centimeters]) and approximately 6 inches (15

centimeters) from the deluge spray sprinkler heads.

14.8.2.4

When automatic deluge spray systems are installed in final filter plenum

enclosures that contain prefilters, water spray deluge sprinkler heads

should be located upstream from the prefilters. In this configuration, the

prefilters act as a demister.

14.8.3

Design of Automatic Deluge Spray Systems

14.8.3.1

Automatic deluge spray systems should be designed per the applicable

provisions of NFPA 13 and NFPA 15, and as follows (see Appendix C):

Density. Water spray density should be 0.25 gpm per sq. ft. over

the entire filter area or 1 gpm per 500 cfm air flow, whichever is

greater.

Sprinkler head type. Spray sprinkler heads should be deluge type

sprinkler heads.

Location from prefilters or demisters. The spray pattern of the deluge

sprinkler head should be in the form of a downward vertical water curtain

approximately 6 inches (15 centimeters) in front of the prefilter or demister.

In addition, deluge sprinkler heads should be spaced so that each

sprinkler head does not exceed 4 lineal feet of curtain coverage.

Activation by detection. Deluge spray sprinkler system should operate

upon activation of fire alarm system heat detectors or pilot sprinkler heads

located in either the final ducting or filter plenum housing. Manual

activation should be provided as well.

14.8.3.2

Automatic water spray system equipment should be listed for its intended

use as required by NFPA 13 and NFPA 15.

14.8.3.3

Existing automatic deluge spray systems that provide equivalent and

reliable fire protection for plenum filtration systems (as determined by past