The time required to replace a damaged coil and clean up the flooded AHU casing with possible contamination from treatment chemicals can put an AHU out of service for a long time—and during the most critical environmental conditions. Water leakage in a casing from a damaged cooling coil can provide an environment suitable for microbial growth and may go undetected for an extended time. The potential impact on a health care facility under such conditions can be very serious and costly. This section discusses some general freeze-prevention considerations and practices.
In many applications, a preheat coil is located downstream from the prefilter and before the cooling coil. If the mixed-air condition during the winter design day is sufficiently above freezing and the unit is configured to allow intake of large quantities of outdoor air such as with a smoke ventilation or economizer system , a preheat coil may not be required. In addition to considering performance under design conditions, designers should think about how the coil should perform under the most severe conditions that it may encounter.
Frequent steam coil freeze failures have resulted from exposure of the condensate-filled portions of the coil to freezing air temperatures. Be aware that modulating steam control valves may cause negative atmospheric pressure in the coil, increasing the volume of condensate backup; providing a vacuum breaker will allow the condensate to drain by gravity. Many designers prefer a face-and-bypass approach for steam coil discharge temperature control, keeping the steam coil control valve fully open any time there is a need for preheat and regulating airflow around the coil to maintain discharge setpoint.
To prevent energy waste, the coil should be fitted with a two-way valve so that the coil can be turned off when preheat is no longer needed.
This arrangement, while undoubtedly successful in many applications, does not necessarily eliminate the danger of condensate buildup in the coil. When hot-water coils are used, designers must decide whether to use an antifreeze solution in the system.
In addition to reducing heat transfer and increasing the pumping energy requirement, there are significant mainte- nance considerations associated with the use of an antifreeze solution. When properly used and designed, however, glycol systems can be a very attractive freeze protection option. For these situations, the system needs enough glycol to keep the fluid from freezing solid. A slushy mixture is acceptable, because the fluid will not be pumped through the system.
Freeze protection is required, however, if a system is going to be pumping the fluid at the lowest anticipated temperature. This can include systems that are dormant for much of the winter but require start-up during cold weather, or systems that would be at risk if the power or pump failed. Trying to pump fluid containing ice crystals can result in damage to system components. For these situations, the system must have enough glycol present to prevent any ice crystals from forming. Because the mixture expands as it freezes, there must be enough volume available in the system to accom- modate the expansion.
It generally requires more glycol for freeze protection keeping the fluid completely liquid than it does for burst protection where a slushy mixture is acceptable. There are several types of glycol available. Many facilities are now using food-grade antifreeze so that system draindowns can be discharged to the sanitary sewer or stormwater system. A circulating pump maintains a continuous flow of water in the coil throughout the heating season. The combination of continuous flow and pump heat can provide a significant degree of freeze protection.
A freezestat is normally located on the upstream face of the cooling coil the location may differ, depending upon AHU design and configuration. Too frequently, how- ever, improper installation of the freezestat has led to damaged coils or nuisance trips.
The freezestat consists of a long length of sensor tubing that must be installed in a serpentine fashion across the entire face of the coil so as to detect any localized freezing temperatures that are caused by air stratification. When inadequate space is provided for sensor installation, the tubing is frequently placed as a coiled bundle, which greatly compromises its effectiveness. For this reason, as well as to enable cleaning the upstream face of the cooling coil, an upstream access panel must be provided, with dimensions suitable to enable a maintenance technician to access the entire face of the coil.
These coils may use antifreeze to reduce the freezing point. In such instances, the preheat leaving temperature would be lower than the desired supply air temperature, so the designer must be careful to select a freezestat with a lower setpoint range. In addition to providing sensible cooling, a cooling coil acts as a 3.
To fulfill this purpose, it must normally have a high heat transfer surface area consisting of at least six tubing rows with relatively tightly spaced fins. Because the heat transfer surfaces essentially remain continuously wet, cooling coils easily collect dust and can become a microbe growth site. For this reason, the ability to clean the coil is extremely important. When additional rows are required, the cooling coil should be split into two separate coils in the direction of airflow, as shown in Figure Both the upstream and downstream faces of the cooling coil s must be accessible to a maintenance worker using a power washer.
To avoid carryover of droplets from the cooling coil into the AHU casing, the air velocity through the cooling coil must be limited. Designers have traditionally targeted a maximum velocity of to fpm [2. Lower initial coil velocities have the added benefit of allowing for future growth and can improve coil performance, as shown in Figure UV radiation disrupts the DNA of a wide variety of microorganisms, thus rendering them harmless.
UV is especially effective at keeping cooling coils and drain pans free of microbial contamination. When used in air- handling systems or ductwork, safety precautions must be taken to protect maintenance staff from exposure to the harmful UV rays and to protect AHU components from damage. Access doors should be fitted with interlocks which will turn off the UV in the event the door is opened. Precaution labels should be posted near access doors to any equipment with UV systems.
Cooling coils must be provided with positively draining pans con- 3. An oversized and Drains condensate drain pan can have an adverse effect and provide locations for microbial growth. Pans should reach entirely beneath the coil and extend approximately 12 in. The pan should be at least 2 in. When coils are stacked vertically, a separately trapped drain pan as in Figure should be provided for each coil. All drain pans must be properly trapped to ensure that the condensate continues to drain during fan operation.
In both cases, maintenance of the trap seal is important to avoid drawing sewage gases into the AHU. Figure shows condensate drain trap details for a coil subjected to negative pressure draw-through and for a coil subjected to positive pressure blow-through.
For coils subjected to negative pressure, unless the trap is properly constructed to provide a positive gravity head on the pan-inlet side such head exceeding the negative pressure imposed by the unit fan condensate will not drain from the unit.
For coils under positive pressure, the outlet leg of the trap must be high enough to offset the positive static pressure on the inlet side, which would otherwise blow out the trap seal. Where possible, the designer may consider bottom outlet drains for improved performance. For wide units. For taller coil banks, the designer should consider multiple drain pans as indicated in Figure Such an arrangement prevents excessive condensate buildup on the lower sections of the coil where carryover may occur.
The as-constructed air system pressure-flow characteristics, and, therefore, the fan operating point, often differ from the calculated values. It is a good idea to ensure that the specified fan motor power is sufficient to provide for fan operation along a broad range of the fan operating curve. Consider the need to attenuate fan-generated noise that may be transmitted through the distribution system to occupied spaces.
Airfoil-bladed centrifugal fans and plenum-style fan arrangements tend to be less noisy than other alternatives. When final filters or coils are located downstream of the fan discharge, a discharge air diffuser may be required depending upon conditions and type of fan to equalize the outlet velocity profile and avoid excessive pressure losses or velocities in the downstream components. Catalog fan performance data are normally based upon laboratory conditions at the fan inlet and outlet, which often cannot be duplicated in the field and which maximize the performance of the fan.
When conditions are less ideal, fan performance will be lower. On the suction side, system effects can result from factors such as restricted inlets, flow obstructions such as bearings or inlet vanes , and air prespin caused by improperly designed elbow connections.
On the discharge side, system effects may result from obstructions by fittings or equipment e. This better accounts for the impact of the AHU casing on fan performance, but does not account for system effects related to the connected ductwork. Some AHU manufacturers may perform the test with several diameters of straight ductwork connected at the discharge, while others may not Page The designer can help reduce system effect by avoiding hard bends, poorly designed turning vanes, improperly designed branch flows, and abrupt AHU inlets or discharge take- offs.
Also, using discharge plenums provided and tested by the AHU manufacturer can avoid elbows or transitions located too close to the fan discharge. The HVAC designer should make the building designer aware that inadequate AHU mechanical room space and shaft location can create problems and reduce system performance and energy efficiency.
The laboratory conditions used to test fans normally involve the fan being driven by a direct-drive dynamometer. Fan selection for a given application requires designer consider- ation of the performance characteristics and space requirements of the various fan types or variants available. Table compares some of the fan types frequently used in hospital AHUs. Phased projects where fans may have to operate at an initial flow condition much lower than the final design point can offer additional challenges.
The designer must review both the initial operating point on the fan curve as well as the final design point to confirm that both conditions are within a stable operating zone for the fan.
Figure shows how an initial operating point could fall into an unstable region if there is not a careful review of the fan selection and curves. Blow-through arrangements are typically seen in dual-duct system or multizone AHUs. Return fans are often required for AHUs that have a ducted return 3. As with the supply fan, consideration must be given to fan noise generation and the need for attenuation to reduce sound transmitted through the return ductwork to occupied spaces.
Ensure that adequate space is available for personnel access to all parts of the return fan that require inspection or periodic maintenance. Fan type selection must consider required performance and equipment space availability for each application. Deep blades allow of velocity pressure to static pressure. Maximum efficiency requires close Airfoil Air leaves impeller at velocity less than clearance and alignment between tip speed.
For given duty, has highest speed of centrifugal fan designs. Single-thickness blades curved or inclined Uses same housing configuration Backward- Inclined Backward- Curved away from direction of rotation. Efficient for same reasons as airfoil fan.
Higher pressure characteristics than airfoil, Scroll similar to and often identical Centrifugal Fans backward-curved, and backward-inclined fans. Radial Tip Rt Radial R Curve may have a break to left of peak Fit between wheel and inlet not as pressure and fan should not be operated critical as for airfoil and backward- in this area. Power rises continually to free delivery. Flatter pressure curve and lower efficiency Scroll similar to and often identical Forward- Curved than the airfoil, backward-curved, and to other centrifugal fan designs.
Fit between wheel and inlet not as Do not rate fan in the pressure curve dip to the critical as for airfoil and backward- left of peak static pressure. Power rises continually toward free delivery.
Plenum and plug fans typically use airfoil, Plenum and plug fans are unique in backward inclined, or backward curved that they operate with no housing. The components of the drive system for the plug fan are located outside the airstream. Low efficiency. Simple circular ring, orifice plate, or venturi. Limited to low-pressure applications. Propeller Optimum design is close to blade tips Usually low-cost impellers have two or and forms smooth airfoil into wheel.
Primary energy transfer by velocity pressure. Somewhat more efficient and capable of Cylindrical tube with close clearance developing more useful static pressure than to blade tips. Axial Fans propeller fan. Tubeaxial Usually has 4 to 8 blades with airfoil or single- thickness cross section. Hub is usually less than half the fan tip diameter. Good blade design gives medium- to high- Cylindrical tube with close clearance pressure capability at good efficiency.
Vaneaxial Most efficient have airfoil blades. Guide vanes upstream or downstream from impeller increase pressure Blades may have fixed, adjustable, or capability and efficiency. Hub is usually greater than half fan tip diameter. Similar to airfoil fan, except peak efficiency Same heating, ventilating, and air-conditioning slightly lower. Curved blades are slightly more efficient than Used in some industrial applications where straight blades. Higher pressure characteristics than airfoil and Primarily for materials handling in industrial plants.
Also for some high-pressure industrial requirements. Pressure may drop suddenly at left of peak pressure, Rugged wheel is simple to repair in the field. Wheel but this usually causes no problems. Curved blades are slightly more efficient than straight blades.
Pressure curve less steep than that of backward- Primarily for low-pressure HVAC applications, curved fans. Curve dips to left of peak pressure. Operate fan to right of peak pressure. Power rises continually to free delivery which is an overloading characteristic.
Other advantages of these fans are discharge They are more susceptible to performance configuration flexibility and potential for smaller- degradation caused by poor installation. High flow rate, but very low pressure capabilities. For low-pressure, high-volume air-moving applications, such as air circulation in a space Maximum efficiency reached near free delivery.
Discharge pattern circular and airstream swirls. Used for makeup air applications. High flow rate, medium pressure capabilities. Low- and medium-pressure ducted HVAC applications where air distribution downstream Pressure curve dips to left of peak pressure. Avoid operating fan in this region. Used in some industrial applications, Discharge pattern circular and airstream rotates such as drying ovens, paint spray booths, or swirls.
High-pressure characteristics with medium-volume General HVAC systems in low-, medium-, flow capabilities. Pressure curve dips to left of peak pressure. Has good downstream air distribution. Guide vanes correct circular motion imparted by Used in industrial applications in place impeller and improve pressure characteristics and of tubeaxial fans.
More compact than centrifugal fans for same duty. Ideally suited in applications a tubular housing and include outlet Mixed-Flow Mixed-Flow in which the air has to flow in or out axially. Higher pressure characteristic than axial fans. Can operate without housing or in a pipe and duct. Impeller with forward-curved blades. Tangential Cross-flow Cross-flow rotor blades into the rotor. This creates an area of turbulence which, working with the guide system, deflects the airflow through another section of the rotor into the discharge duct of the fan casing.
Lowest efficiency of any type of fan. Performance similar to backward-curved fan Cylindrical tube similar to vaneaxial fan, Tubular Centrifugal except capacity and pressure are lower. Lower efficiency than backward-curved fan. Performance curve may have a dip to the left of peak pressure. Low-pressure exhaust systems such as Normal housing not used, because air general factory, kitchen, warehouse, and some dis- charges from impeller in full circle.
Centrifugal Other Designs Usually does not include configuration to Provides positive exhaust ventilation, which recover velocity pressure component. Power Roof Ventilators Centrifugal units are slightly quieter than axial units. Low-pressure exhaust systems such as Essentially a propeller fan mounted in a general factory, kitchen, warehouse, and some supporting structure.
Air discharges from annular space at bottom Axial Provides positive exhaust ventilation, which of weather hood. Hood protects fan from weather and acts as safety guard. For normal operation, the relief fan can often remain off, and the supply fan provides the pressure differential for both return and supply ductwork. The complexities of humidifier design and maintenance are often underestimated by designers, with the result that the devices are frequently disconnected by maintenance personnel or cited as a cause of contamination and corrosion within the AHU or ductwork.
Leaks and other malfunctions resulting in oversaturated air are common. Designers must carefully consider the selection, loca- tion, and control of humidifiers within AHUs or ductwork to avoid moisture accumulation in downstream components, including filters and insulation. Higher pressure than axial fans and in applications where an axial fan cannot generate higher volume flow than centrifugal fans.
Similar to forward-curved fans. Power rises Low-pressure HVAC systems such as fan heaters, continually to free delivery, which is an overloading fireplace inserts, electronic cooling, and air curtains. Unlike all other fans, performance curves include motor characteristics.
Lowest efficiency of any fan type. Performance similar to backward-curved fan, except Primarily for low-pressure, return air systems capacity and pressure are lower.
Lower efficiency than backward-curved fan because Has straight-through flow. Performance curve of some designs is similar to axial flow fan and dips to left of peak pressure. Usually operated without ductwork; therefore, Centrifugal units are somewhat quieter than operates at very low pressure and high volume. Low-pressure exhaust systems, such as general factory, kitchen, warehouse, and some commercial installations.
Low first cost and low operating cost give an advantage over gravity-flow exhaust systems. Usually operated without ductwork; therefore, Low-pressure exhaust systems, such as general operates at very low pressure and high volume. They are not intended to provide complete selection criteria, because other parameters, such as diameter and speed, are not defined.
Steam is sterile and, therefore, eliminates the risk of introducing viable microorganisms, such as Legionella, into the building airstream. Steam may be generated centrally using a boiler or heat exchanger or locally at the humidifier by a separate electrical or steam-to-steam generator.
Small gas-fired units are also available. Regardless of the steam source, care must be taken to ensure that only dry steam is supplied to the steam injector.
Unless a suitable expanse of downstream duct or AHU casing is provided to allow for reevaporation, the mist will impinge on downstream equipment and cause water buildup. Filters, exposed insulating materials, and even sheet metal can easily become microbe growth sites in these circumstances, and fans and other steel AHU and ductwork components will quickly rust.
The distance required for reevaporation is a function of air temperature, relative humidity, velocity, casing or duct dimensions, and the design of the humidifier components; it can vary from a few inches several mm to more than 12 ft [3. Consider placing the humidifier upstream of the cooling coil.
The supply air is warmer at this point, which will improve absorption. This location also allows the cooling coil fins to act as an eliminator blade section and provide an additional safeguard to prevent wetting of downstream components such as fans and filters. The control measuring point should be located downstream from the cooling coil to prevent oversaturation of the air entering the coil.
Sensors and controls must be kept in proper working order and calibration to prevent energy waste by oversaturation of the air and subsequent dehumidifying with the cooling coil. Note that, although dehumidification occurring in the cooling coil could result in wasted energy, this is better than potentially wetting a downstream filter section that would compromise infection control. The humidifier steam discharge relative to the airflow direction depends on the particular manu- facturer.
Humidifiers are often controlled by a space humidistat or a return air sensor. Such a control approach can introduce the opportunity for oversaturation of supply air. Designers should consider controlling the humidifier from a supply air sensor instead. Room humidistats or return air sensors can still be used but would not directly control the humidifier. A call for additional humidity from a room humidistat or return air sensor would instead increase the supply air humidity setpoint.
Users should not be given control of humidity from room humidistats. Many of the spaces in a health care facility require a higher level of 3. Some codes require HEPA filtration for inpatient applications, especially where patients are particularly vulnerable to infection, such as protective isolation rooms for immunocompromised patients and orthopedic operating rooms.
Designers must provide and require in contract documents adequate space for replacing filters. All filters should be provided with a differ- ential pressure indicating manometer, mounted on the AHU, to indicate when replacement is required. Electronic monitoring through the building automation system is highly desirable.
Automatic alarms can be included to alert maintenance personnel of the need for a filter change. The design air velocity for health care facility AHU filters should not exceed fpm [2. If no final resistance recommendation is available, a value of 1. Be aware that when filters are clean, resulting in system resistance lower than the fan selection point, the fan motor must be adequately sized to accommodate the higher power requirements at that operating condition.
One advantage of using variable-speed drives on fans is that fan speed can be increased as filters begin to load so the AHU maintains a constant airflow. Figure shows a typical relationship of pressure drop versus air velocity for a MERV 14 filter.
Improper filter racks allow air to leak past and bypass the filters. MERV 14 and up filters are available in both bag and cartridge style. Cartridge filters are becoming very popular because of their increased durability. This is often a concern with the double-walled AHUs required for health care facilities, because the interior sheet metal wall resists noise breakout and helps to transmit the noise through the duct- work. Providing sidewall takeoffs where diffusers connect to ductwork and adding flexible ductwork with at least one elbow at final diffuser or grille connections can offer significant attenuation.
Packless type attenu- ators and active silencers have limited application and efficacy, often leaving packed-type liners and attenuators as the only practical choice. This chapter has already discussed concerns regarding water-perme- able, unsealed insulation surfaces exposed to the airstream. Such foil or plastic liners do not drastically reduce attenu- ation performance.
Because of installation space limitations, and to improve the inspectability and cleanability of airflow surfaces, fabricated attenuators are often chosen over attenuating ductwork.
Attenuator inlet and outlet conditions must also be considered. Many designers do not realize that, without proper transitions, the pressure loss across a sound attenuator can be several times the catalog value and the device can actually generate more noise than it attenuates. The designer needs to include suitable transition space and provide appropriate details and instructions for the contractor.
As indicated in that chapter, many of the most sensitive areas can be found in the health care environment. Such areas include operating rooms, microsurgery areas such as eye surgery , labs using electron microscopes, and laser equipment locations.
In addition to the methods covered in the Handbook chapter, the designer can follow some simple practical design guidelines to avoid potential vibration issues. Airflow-monitoring arrays are often provided in the return and 3. This monitoring can help the owner confirm that minimum ventilation rates are being maintained and alarm the owner of potential energy waste when excessive outdoor air is being introduced because of malfunctioning dampers or controls. To accurately measure velocity and therefore flow volume , monitoring arrays require a reasonably uniform entering velocity profile.
Establishing that profile normally requires a certain extent of straight upstream ductwork usually specified by the device manufacturer in terms of unit diameters and a smoothly transitioning discharge arrangement.
Very stringent upper limit relative humidity requirements may, however, dictate supplemental dehumidification using mechanical refrigeration or desiccant equipment. Some designers address this issue by providing automatic controls to reset the cooling coil discharge temperature below that required for cooling as a means of providing dehumidification; such a strategy requires reheat of the air supply for comfort conditioning.
This control strategy can be difficult to accomplish with a nonmodulating cooling system, such as traditional direct-expansion DX systems. When such a control strategy is needed, and chilled water is not available, the designer should consider special DX systems that are designed to operate in a reheat mode. Several manufacturers offer such systems, which use hot-gas bypass or variable-speed compressors to modulate the cooling capacity and maintain fixed discharge temperatures. Refer to section 3.
Most areas operate 24 hours per day. Shutdown of an AHU not only compromises patient and staff comfort but also compromises infection control because of loss of pressure rela- tionships for critical spaces.
In some critical areas, such as operating rooms, central sterile supply, isolation rooms, and areas accommodat- ing immunocompromised patients such as a bone marrow unit , even a momentary loss of supply air presents a problem. For such areas, the designer should consider redundant equipment. Dual units operating in parallel might be considered.
Figure illustrates a configuration often used with hospital AHUs. High-pressure dampers are provided to isolate one side and prevent backflow of air through that section when it is down for service. For all of the systems listed below, terminal boxes or devices should have double- wall construction or insulation lined with foil or polyester film to avoid exposed insulation in the airstream.
Factory-mounted access doors to inspect dampers and coils are a relatively low-cost option and are useful for maintenance and troubleshooting. Access doors should include gaskets and good locks for a tight seal. Adding a supply air temperature sensor in the leaving airstream provides a very useful monitoring point for diagnosing system problems. Locate terminal boxes where they can be easily accessed for service and maintenance.
Avoid locations above light fixtures, walls, work areas, patient care areas, or other spaces that will restrict access. Consider the controller location as well and maintain sufficient clearance for service. Although some interior locations VAV Systems may not, in theory, require heating, the designer should consider including reheat for rapid warm-up when thermostat settings are raised. Consider that patients are often sensitive to low room temperatures and drafts.
When using VAV systems, minimum airflow settings must be sufficient to meet minimum air exchange rates for both outdoor and supply air.
VAV terminal boxes without reheat are a good solution for spaces such as equipment rooms, electrical rooms, and other typically unoccupied areas that have continuous internal loads and do not require heat. Because these spaces do not have required minimum air exchange rates or outdoor ventilation air requirements, minimum airflow can be set to zero, thereby eliminating the need for reheat. Variable-air-volume systems with reheat are common in hospital 3.
Reheat coils should be sized to provide rapid warm-up as well Terminal Reheat as to meet the steady-state load. This is especially true in areas, such VAVTR Systems as operating rooms, where very rapid temperature changes are desired.
In some cases, operating rooms may require high room temperatures during surgical procedures. Two-row heating coils for reheat will also provide more capacity for rapid warm-up and to meet high room temperature requirements. As with VAV systems, VAVTR systems must also maintain minimum airflow settings sufficient to meet mini- mum air exchange rates for both outdoor and supply air.
Although room pressure requirements or high air exchange requirements may suggest a CAV system, there must be a means to maintain temperature when cooling loads in the various spaces are lower than peak design.
For this reason, CAV terminal reheat systems are more common in the hospital environment. In such areas, there may not be an opportunity to use a VAVTR system, or the amount of peak airflow that can be varied may be too low to justify the added com- plexity of a VAVTR system. CAVTR systems may also be considered for areas where maintaining room pressure is critical e. This is no longer the case for new hospitals because of the additional cost and space requirements of dual primary air supply ducts.
Many older systems are still in place, and the hospital designer may be tasked with renovations or expansions of these systems. A problem frequently encountered in older dual-duct systems is poor control, or leaking of air from the primary air source that is being set back. For example, with a dual-duct terminal box in full cooling mode where the hot-duct air should be at minimum or zero, a poorly functioning diverting damper or hot-duct damper may cause unwanted hot air to continue flowing, thus significantly reducing cooling capacity.
When renovating or expanding such systems, the designer may want to consider repair or replacement of existing terminal boxes. AHU repairs or modifications such as variable-speed fan drives or discharge dampers will reduce overpressurization of ductwork and assist in preventing this leakage. These were particularly popular in patient rooms.
While not expressly prohibited for use in patient care areas, it can be difficult to meet many of the current codes and standards with these systems. Many state and local codes require that these units be noncon— densing. In such circumstances, additional systems must be used to provide latent cooling for the spaces.
Chilled beams are another type of room recirculating terminal unit. Chilled beams consist of two types, passive and active. Passive beams use only a heat exchanger coil; there is no connection for a primary air system. Air movement through the cooling coil in the beam is induced by natural convection.
A separate system must be used for ventilation. Active beams work much like an induction unit. Primary air is supplied to the unit and discharged through high-velocity nozzles that induce airflow through the terminal.
A heat exchanger coil in the beam provides heating or cooling. This coil must be kept clean to maximize performance. Dfsign air need not be exhausted if darkroom equipment has scavenging exhaust duct attached and meets ventilation standards regarding NIOSH, OSHA, desitn local employee exposure limits. As only part of the space is radiated, many authorities question the effectiveness of upper-level UVGI.
ICU spaces today are specialized. Airflow into a space negative pressurization is utilized when it is desired to prevent contaminants released in the space from spreading to adjoining areas. Heat release information is often available from equipment manufacturers, and information on the frequency of usage may come from the eventual equipment user. As a rule, environmental control requirements and the relative role of the HVAC system in life safety and infection control become more important with increasing complexity of the medical services provided and the degree of illness of the patient population.
The empty bags are returned as verification of administration and for billing. Amplification reproduction within HVAC airflow equipment, especially areas where hospitzls and dirt can accumulate, such as cooling coil drain pans, wet filters, and porous duct linings exposed to direct moisture.
Outpatient surgical facilities usually are Class A facilities and may, under certain circumstances, be Class B facilities. The risk of infection is not limited to patients. I have included a list of current committee members and other contributors. The Microbiology Laboratory provides tests in bacteriology, virology, parasitology, mycobacteriology, mycology, and infectious diseases serology. Fundamentals of Industrial Hygiene. Mechanical ventilation is ventilation provided by mechanically powered equipment such as motordriven fans and blowers, not by devices such as wind-driven turbine ventilators and mechanically operated windows.
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Year Edition 2. Number of Pages
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