Question

write a surmmary:

5.4.2 Applying External Filtration

Applying external filtration to a building requires modifica- tions to the building’s HVAC system and electrical system, and it also usually requires minor architectural changes to reduce air leakage from the selected protective envelope. These changes are necessary to ensure that, when the protective system is in operation, all outside air enters the building through the filters. The air exchange that normally occurs due to wind, chimney effect, and operation of fans must be reduced to zero. This is achieved mainly by introducing filtered air at a rate sufficient to produce an overpressure in the building and create an outward flow through all cracks, pores, seams, and other openings in the building envelope. For standby systems, dampers are normally required to tighten the envelope in transitioning to the protec- tive mode. The level of overpressure required varies with weather conditions and height of the building.The capacity of filtration units needed for protection is determined by the leakage characteristics and size of the building. The cost of installing a high efficiency filtration system varies directly with the leakage rate; higher leakage rate equals higher costs, and the need for additional heating and cooling capacity for the filtered air.Filtration system capacity must be matched to the leakage of the building to achieve maximum protection. Fan-pressurization tests are usually performed on buildings to determine their normalized leakage rates. Nominal data on the leakage rates of various types of buildings are available in the U.S. Army Corps of Engineers Engineering Technical Letter (ETL) 1110-3-498, Design of Collec- tive Protection Shelters to Resist Chemical, Biological, and Radiological (CBR) Agents, (February 24, 1999) and can be used to estimate the leakage rate of a building.

Answer 1

A Building’s HVAC system and electrical system requires modification when we apply external filtration to it and it also usually requires minor architectural changes to reduce air leakage.These changes ensure that, when the protective system is in operation, all outside air enters the building through the filters.The air exchange that normally occurs due to wind, chimney effect, and operation of fans must be reduced to zero.This is achieved by introducing filtered air at a rate sufficient to produce an over pressure in the building and create an outward flow through all cracks, pores, seams, and other openings in the building envelope. For standby systems, dampers are normally required to tighten the envelope in transitioning to the protective mode.The cost of installing a high efficiency filtration system depends directly on the leakage rate.Filtration system capacity must be matched to the leakage of the building to achieve maximum protection.