CHAPTER 4 VENTILATION - iccsafe.org

1 CHAPTER 4 VENTILATIONSECTION CHAPTER shall govern the VENTILATION ofspaces within a building intended to be occupied. This chapterdoes not govern the requirements for smoke control principles specified in ASHRAE Standard 62-2001 maybe used as an alternate to this CHAPTER to demonstrate compli-ance with required VENTILATION air for VENTILATION occupied space shall beventilated by natural means in accordance with CHAPTER 12 oftheBuilding Codeor by mechanical means in accordance withSection When shall be provided during theperiods that the room or space is Opening air exhaust and intake open-ings shall be located a minimum of 10 feet (3048 mm) from lotlines or buildings on the same lot.

2 Where openings front on astreet or public way, the distance shall be measured to the cen-terline of the street or public :1. Group Exhaust outlets for environmental air exhaust open-ings shall be located not less than 3 feet (914 mm)from property lines and not less than 3 feet (914 mm)from openings into the Intake and gravity outdoorair intake openings shall be located a minimum of 10 feet(3048 mm) horizontally from any hazardous or noxiouscontaminant source, such as vents, chimneys, plumbingvents, streets, alleys, parking lots, gas meters and loadingdocks, except as otherwise specified in this code. Where asource of contaminant is located within 10 feet (3048 mm)horizontally of an intake opening, such opening shall belocated a minimum of 2 feet (610 mm) below the contami-nant exhaust from a bathroom or kitchen in a residentialdwelling shall not be considered to be a hazardous or nox-ious Exhaust exhaust openings shallbe located so as not to create a nuisance.

3 Exhaust air shallnot be directed onto Flood structures located in flood haz-ard areas, outdoor exhaust openings shall be at or above thedesign flood Outdoor opening exhaust and intakeopenings that terminate outdoors shall be protected with corro-sion-resistant screens, louvers or grilles. Openings in louvers,grilles and screens shall be sized in accordance with , and shall be protected against local weather air exhaust and intake openings located in exteriorwalls shall meet the provisions for exterior wall openingprotectives in accordance with theBuilding SIZES IN LOUVERS, GRILLES ANDSCREENS PROTECTING OUTDOOR EXHAUSTAND AIR INTAKE OPENINGSOUTDOOR OPENING TYPEMINIMUM AND MAXIMUM OPENINGSIZES IN LOUVERS, GRILLES ANDSCREENS MEASURED IN ANYDIRECTIONE xhaust openingsNot<1/4inch and not>1/2inchIntake openings in residentialoccupanciesNot<1/4inch and not>1/2inchIntake openings in other thanresidential occupancies>1/4inch and not>1 inchFor SI.

4 1 inch = Contaminant local sources produc-ing air-borne particulates, heat, odors, fumes, spray, vapors,smoke or gases in such quantities as to be irritating or injuriousto health shall be provided with an exhaust system in accor-dance with CHAPTER 5 or a means of collection and removal ofthe contaminants. Such exhaust shall discharge directly to anapproved location at the exterior of the 402 NATURAL VENTILATION (See CHAPTER 12 of theOregon Structural Specialty Code)SECTION 403 MECHANICAL VENTILATION VENTILATION shall be pro-vided by a method of supply air and return or exhaust air. Theamount of supply air shall be approximately equal to theamount of return and exhaust air.

5 The system shall not be pro-hibited from producing negative or positive pressure. The sys-tem to convey VENTILATION air shall be designed and installed inaccordance with CHAPTER supply systems shall be designed to deliver therequired rate of supply air to the occupied zone within an occu-pied space. The occupied zone shall have boundaries measuredat 3 inches (76 mm) and 72 inches (1829 mm) above the floorand 24 inches (610 mm) from the enclosing OREGON MECHANICAL SPECIALTY CODE31 Note:Heating and air conditioning controls shall conform to Chap-ter 13 of theOregon Structural Specialty :\data\CODES\STATE CODES\Oregon\2007\Mechanical Custom Code\Final VP_Chgo\ , December 29, 2006 11:36:58 AMColor profile: Generic CMYK printer profileComposite Default Outdoor air minimum VENTILATION rate ofoutdoor air shall be determined in accordance with.

6 Where the registered design professional dem-onstrates that an engineered VENTILATION system design willprevent the maximum concentration of contaminants fromexceeding that obtainable by the rate of outdoor air ventila-tion determined in accordance with Section , the mini-mum required rate of outdoor air shall be reduced inaccordance with such engineered system Recirculation of air required by shall not be recirculated. Air in excess of that required bySection shall not be prohibited from being recirculatedas a component of supply air to building spaces, except that:1. VENTILATION air shall not be recirculated from onedwelling to another or to dissimilar Supply air to a swimming pool and associated deckareas shall not be recirculated unless such air is dehu-midified to maintain the relative humidity of the areaat 60 percent or less.

7 Air from this area shall not berecirculated to other spaces where 10 percent or moreof the resulting supply airstream consists of airrecirculated from these Where mechanical exhaust is required by Note b inTable , recirculation of air from such spacesshall be prohibited. All air supplied to such spacesshall be exhausted, including any air in excess of thatrequired by Table Where mechanical exhaust is required by Note h inTable , mechanical exhaust is required andrecirculation is prohibited where 10 percent or moreof the resulting supply airstream consists of airrecirculated from these Transfer transferred from occupied spaces isnot prohibited from serving as makeup air for requiredexhaust systems in such spaces as kitchens, baths, toiletrooms, elevators and smoking lounges.

8 The amount of trans-fer air and exhaust air shall be sufficient to provide the flowrates as specified in Sections and The requiredoutdoor air rates specified in Table shall be introduceddirectly into such spaces orinto the occupied spaces fromwhich air is transferred or a combination of :1. Where recirculation from such spaces is prohib-ited by Table Air transferred from spaces served by other fansystems shall not be used if those systems arerequired to meet either Section of this codeor Section or of theOregon Struc-tural Specialty Where the VENTILATION schedule of HVAC systemsupplying transfer air is not similar to the exhaustsystem operating VENTILATION systems shall be designed tohave the capacity to supply the minimum outdoor airflow ratedetermined in accordance with Table based on the occu-pancy of the space and the occupant load or other parameter asstated therein.

9 The occupant load utilized for design of the venti-lation system shall be based on expected average occupant loadprovided the average occupant load is not less than one-half thenumber determined from the estimated maximum occupant loadrate indicated in Table The anticipated VENTILATION occu-pancy load and occupancy VENTILATION design methods shall bedocumented on plans and specifications. The VENTILATION systemshall be designed to supply the required rate of VENTILATION aircontinuously during the period the building is occupied, exceptas otherwise stated in other provisions of the :The occupant load is not required to be deter-mined, based on the estimated maximum occupant load rateindicated in Table where approved statistical data docu-ment the accuracy of an alternate anticipated occupant System minimum flow rate of out-door air that the VENTILATION system must be capable of sup-plying during its operation shall be permitted to be based onthe rate per person indicated in Table and the actualnumber of occupants Common VENTILATION spaces hav-ing different VENTILATION rate requirements are served by acommon VENTILATION system.

10 The ratio of outdoor air to totalsupply air for the system shall be determined based on thespace having the largest outdoor air requirement or shall bedetermined in accordance with the following formula:()YXXZ=+ 1(Equation 4-1)whereY=Vot/Vst= Corrected fraction of outdoor air in Uncorrected fraction of outdoor air in sys-tem Fraction of outdoor air in critical space. Thecritical space is that space with the greatestrequired fraction of outdoor air in the supplyto this Corrected total outdoor airflow Total supply flow rate, , the sum of all supply forall branches of the Sum of outdoor airflow rates for all branches on Outdoor airflow rate required in critical Supply flow rate in critical Variable air volume system airvolume air distribution systems, other than those designedto supply only 100-percent outdoor air, shall be providedwith controls to regulate the flow of outdoor air.