Some drinking water contaminants may be harmful if consumed at certain levels in drinking water while others may be harmless. If this air pressure field within the partition wall is also negative with respect to the exterior, it leads to the infiltration of hot humid air during cooling periods and contaminants during other periods through the exterior wall assembly, down the demising wall to the dropped ceiling assembly (Figure 12). During cooling periods when this air is cooled due to the cooling of the hotel rooms on both sides of the partition wall, moisture is deposited in the wall cavities leading to mold and microbial contamination. This negative air pressure field extends to the exterior wall and may or may not be negative with respect to the exterior. In a similar manner to the fan coil unit induced interstitial partition wall depressurization, leakage of the central exhaust duct located within the plumbing service shaft also leads to the creation of a negative air pressure field relative to the rooms in the opposite demising wall that also extends to the exterior wall. This is clearly not the case in the examples in Figures 12 and 13 where air flow is extracted at an intermediate location (the partition wall cavity) due to leakage of the dropped ceiling plenum containing the fan coil and due to central exhaust duct leakage.

As fiberglass batt insulation provides very small resistance to air flow, the connected wall cavity construction in both interior and exterior walls permits considering these walls as acting as air ducts. In exterior walls, fiberglass batt insulation is installed. A typical example is that of exhaust fans pulling air from bathrooms and discharging it to the exterior. This negative air pressure field exists only when the roof top exhaust fan operates and again exists despite the positive air pressure in the hotel room (Figure 13). When the bathroom door is closed, the flow path from the suite to the exhaust grill in the bathroom is interrupted creating a flow resistance resulting in more air to be extracted from the partition wall. It also leads to elevated levels of air borne moisture within the room. The air extraction from the partition wall cavities leads to replacement air (make-up air) for the partition wall cavities drawn from the exterior as well as from the rooms on both sides of the partition walls. However, moisture in the infiltrating air is deposited on the gypsum board surfaces enclosing the partition wall interstitial cavity.

Demising wall cavity pulled negative due to connection to dropped ceiling return plenum. These perforations create a connected wall cavity in both interior and exterior walls. The partition wall is further connected to the exterior wall. A negative air pressure field is created in the partition wall relative to the rooms on both sides due to its connection to the dropped ceiling plenum. However, dropped ceiling enclosures are seldom air tight due to numerous penetrations for controls, power supply, and piping. The dropped ceiling enclosure is connected to the partition wall via the penetrations for controls, power supply, piping and through openings reflective of the prevailing construction practice. The partition wall on the opposite side of the room varies between a positive air pressure of 1 Pa. Room is at positive air pressure relative to exterior-driven air from corridor and air supplied to room from fan-coil unit pulling air from exterior through demising wall. This results in increased depressurization within the partition wall on a cycle matched to the opening and closing of the bathroom door.

2 Pa. This pressure fluctuates based on the opening and closing of the bathroom door. The negative air pressure field due to the roof top exhaust fan (as modified by bathroom door closure) may or may not be negative with respect to the exterior. This causes fluctuation in the positive pressure (with respect to the exterior) in the room in synchronization with the duty cycle of the fan-coil. However, it will not lead to an increase in the levels of air borne moisture within the room since the flow path of this infiltrating air is to the plumbing service shaft and subsequently out of the building via the roof top exhaust fan. This outside air supply tends to increase the positive air pressure in the room with respect to the exterior. How do you increase horsepower? OXIRA units have been developed to provide a convenient source of UV and Ozone to help clean your air.