AMAZON multi-meters discounts AMAZON oscilloscope discounts Basic Types Buildings must be ventilated to maintain a healthy and comfortable environment. It is necessary to introduce outside air into a space to replenish oxygen, remove unpleasant odors, and dilute concentrations of water vapor, CO2, and other indoor air pollutants. Ventilation is a combination of processes that results in the supply and removal of air from inside a building. These processes typically include bringing in outdoor air, exhausting some indoor air to the outdoors, conditioning and mixing out door air with indoor air, and distributing the mixed air through out the building. Inadequate ventilation in a densely occupied building space can cause the level of CO2 to increase, leading to occupant sleepiness and reduced efficiency at school and work; with other pollutants it can result it can adversely influence comfort and short- and long-term health. Natural ventilation occurs when the air in a space is changed with outdoor air without the use mechanical systems, such as a fan. This type of ventilation occurs naturally through infiltration of outdoor air-that is, by air leakage through small cracks in the building's envelope, especially around windows and doors. It can also be achieved through temperature and pressure differences between spaces. Such random and uncontrolled ventilation may be sufficient for some buildings (such as some residences), but is not acceptable for most buildings, especially those with large numbers of occupants such as offices, schools, and theaters. In industrial plants, ventilation systems must also remove hazardous airborne contaminants from the workplace. Restaurants require extra ventilation to make up exhaust air needed to remove fumes in the cooking area. Mechanical ventilation, sometimes simple referred to simply as ventilation in the HVAC industry (i.e., the V in HVAC), is the intentional movement of air from outside a building to the inside. A ventilation system typically works in combination with the heating and /or cooling system, but can work separately. Simple ventilation devices include fans or blowers that are arranged either to exhaust the stale indoor air from the building or to force outdoor air into the building, or both. Ventilating systems may be combined with heaters, filters, humidity controls, or cooling devices. Modern HVAC systems and separate ventilation systems include heat exchangers to improve effectiveness. Heat exchangers use outgoing exhaust air to heat or cool incoming outdoor air, thereby increasing the efficiency of the system by reducing the amount of energy needed to operate it. In its recent standard, ASHRAE addresses recirculating reconditioned air in specific spaces. Air within individual building spaces is now classified into one of four classes (Class 1-4). The higher the potential for the air in a space to have odors or contaminants, the higher the numerical classification of the space. For example, a break room that is expected to have relatively few odors or contaminants is a Class 1 space; a private toilet would be a Class 2 space; a room for storage of soiled laundry would be a Class 3 space; and a chemical storage room would be a Class 4 space. There are of course exceptions, but the general concept is that recirculating air from numerically higher class spaces into lower class spaces is not acceptable. Nor is it acceptable to recondition and recirculate Class 4 air back into the space from which it came. ASHRAE Standard 62 The amount of ventilation air required is established by building codes and industry standards. ASHRAE Standard 62 is a standard that outlines ventilation requirements for acceptable indoor air quality that has existed for three decades. Standard 62 has undergone some key changes over the years, reflecting improvements in knowledge, experience, and re search related to ventilation and air quality. Although the purpose of the standard has remained consistent-to specify minimum ventilation rates and other measures intended to provide indoor air quality that is acceptable to human occupants and that minimizes adverse health effects-the methods of achieving this goal have evolved. The latest editions of ASHRAE Standard 62 include: • Standard 62.1-2007 Ventilation for Acceptable Indoor Air Quality • Standard 62.2-2007 Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings Most building codes reference these standards either in part or in entirety, as the minimum requirement for ventilation system design. Standard 62 specifies minimum ventilation rates and IAQ that will be acceptable to occupants in most types of facilities. According to Standard 62, the specified rates at which outdoor air must be supplied to each room is within the range of 15 to 60 cubic feet per minute (ft^3 /min or cfm)/person (7.5 to 30 L/s per person), depending on the activities that normally occur in that room. The need for this amount of ventilation generally dictates mechanical devices such as fans and blowers to supplement the natural flow of air. Tables 3.13 and 3.14 provide an example of outdoor (ventilation) air requirements for selected occupancies. TBL. 13 OUTDOOR (VENTILATION) AIR REQUIREMENTS FOR SELECTED OCCUPANCIES. Occupied Space Facility/Application Commercial Food/beverage Hotel, motel, dorm Office Public spaces Retail store, showroom Institutional Education Residential Private dwellings Space Type: Bar, cocktail lounge Dining room, cafeteria, fast food Kitchen Baths Bedroom, living room Gambling casinos Conference rooms Lobbies, assembly rooms, dorm sleep areas Office spaces, conference rooms Reception areas Elevators Locker rooms, dressing rooms Corridors, utility rooms Smoking lounge Public restrooms Basement and street Upper floors, dressing rooms Malls, arcades Storage rooms, shipping and receiving Warehouse spaces Ticket booths, lobbies Auditorium, stages Corridors Laboratories, training shops Classrooms, music rooms Libraries, auditoriums Autopsy rooms Operating rooms Patient rooms Medical procedure, recovery, intensive care 1 unit, therapy Living areas Kitchens Baths, toilet rooms TBL. 14 REQUIRED MINIMUM VENTILATION RATE IN CFM PER PERSON FOR THE 2006 INTERNATIONAL MECHANICAL CODE and ASHRAE STANDARD 62.1-2007. METRIC (SI) UNITS ARE APPROXIMATE. Occupancy Category: International Mechanical Code | ASHRAE Standard 62.1 Educational classroom (students ages 5-8) Educational classroom (students age 9-up) General or office conference room 2 Hotel, motel, resort, and dormitory lobbies 1 Office building office space 2 Public assembly space or theater auditorium 1 Prev.: Indoor Air Quality |