Medical Construction & Design (MCD) is the industry's leading source for news and information and reaches all disciplines involved in the healthcare construction and design process.
Issue link: https://mcdmag.epubxp.com/i/827184
MCDM AG.COM | M AY/ J U N E 2017 | Medical Construction & Design 51 and increase horsepower requirements. > Floor penetrations: According to NFPA, all fl oor penetrations must be sealed. If not done properly, room pres- sure problems can be created. > Pressure losses: Supply ductwork velocities should not exceed 2500 FPM and return ductwork velocities should not exceed 1500 FPM. The maximum velocity specifi ca- tions should be part of the owner's project requirements. All transitions and turns should be installed with the minimum pressure loss. Operating rooms Operating room suites should maintain a positive pressure of .05" WC (125 Pa) to the transfer corridor and the transfer cor- ridor should be controlled to maintain a positive pressure to the hospital of .05" WC. The operating room should maintain a positive pressure of .02" WC (50 Pa) to the sterile corridors and the sterile corri- dor should maintain a positive pressure of .02" WC to the transfer corridor. The standards recommend all components serving the operating rooms and sterile corridors be located in the transfer corridor ceilings. These components include air valves, coils, automatic and smoke dampers, humidifi ers and airfl ow measuring stations. For eff ective and compli- ant energy conservation, the recommendations for unoccu- pied mode in operating rooms include a reduction in the sup- ply airfl ow to eight air changes per hour and the return to four ACH, which will maintain the room off set constant and allow the pressure balance to remain the same. The standard operating procedure should be written to activate the unoccupied mode when the occupancy switch is in the off position, and activate the occupied mode when the occupancy switch is on (this could be a master light switch or a separate switch). It is strongly recommended that the nursing staff be consulted during design to incorporate their suggestions regarding the location of the switches and when the rooms can be considered unoccupied. Airborne infection isolation rooms Airborne infection isolation room regulation has long been a fi xture of attention, but has been recently subjected to public and media scrutiny in response to highly publicized events. These rooms are required by ASHRAE Standard 170 to have 12 ACH of exhaust and two ACH of outside air. Standards recommend that the rooms be controlled to maintain a negative pressure to the adjacent corridor of .05" WC. If an ante room is used, it likewise should maintain a negative pressure of .05" WC to the adjacent corridor, and the room be controlled to maintain a negative pressure to the hos- pital corridor of .05" WC. To accomplish these pres- sures, the rooms require hard ceilings, doors with astragal seals and door sweeps, and all electrical conduits and boxes shall be sealed. The standards suggest AII rooms be pres- sure tested according to the procedures outlined in the document's chapter on leakage testing. Prior to working in an AII room, the facility's safety department must decontami- nate the room using standard operating procedures and in accordance with the Centers for Disease Control guidance. The standards also provide information specifying the time necessary to ventilate an isola- tion room or area for a given air change per hour before allow- ing employees to enter without respiratory protection. Protective environment rooms Protective environment rooms for high-risk patients, those whose immunity capabilities have been compromised, are to be positively pressurized to all adjoining spaces. Recirculation HEPA fi lters are permitted to increase the equivalent room air exchanges, however, the outdoor air changes are still required. Constant volume air- fl ow is required for consistent ventilation for the protective environment. PE rooms are required by ASHRAE Standard 170 to have 12 ACH of supply and two ACH of outside air. Supply air diff users shall be above the patient bed, unless it can be demonstrated that such a loca- tion is not practical. The room is required to have four ACH of return air. Following the NIH Certifi cation Requirements for room pressure, the stan- dards recommend the PE room be controlled to main- tain a positive pressure to the hospital corridor of .05" WC. Accomplishing this requires hard ceilings, doors with astragal seals, door sweeps and that all electrical conduits and boxes are sealed. PE rooms should be pressure tested by the methods described in the standards. Filtration Many hospital air-handling units and exhaust systems use fi ltration systems that have in excess of 1.0" WC initial pres- sure drop. The pressure dou- bles when the fi lters become dirty. It is recommended to test systems at maximum airfl ow and dirty fi lter conditions to verify the system will provide design airfl ow and specifi es procedures for simulating dirty fi lter conditions. ASHRAE Standard 170 requires air-handling units in hospitals serving Class B and C surgery areas; inpatient and ambulatory diagnostic and therapeutic radiology; inpatient delivery and recovery spaces; inpatient care, treatment and diagnosis areas and spaces provide clean supplies and clean processing using MERV 14 or greater fi lters in the fi nal fi lter location. In blow-through air-handling units, 100 percent saturated air blows directly into the fi nal fi lters and loads the fi lter with moisture. The standards recommend draw through air-handling units be used to elevate the dry bulb temperature of the air above saturation by adding the motor heat and heat of compression to the airstream. A properly balanced build- ing produces occupant com- fort, enhances productivity and well-being, helps maintain the mechanical health of the build- ing and reduces its operating costs. Total system balance promotes an atmosphere for healing and should be an in- tegral element of the facility's management plan. Gaylon Richardson, TBE, CxA, is presi- dent of Engineered Air Balance Co., Inc. and chairman of the Associated Air Balance Council Standards Committee. Photo: Nostal6ie/Dreamstime