Ventilation is the intentional introduction of outdoor air into a space. Ventilation is mainly used to control

indoor air quality Indoor air quality (IAQ) is the air quality within buildings and Nonbuilding structure, structures. Poor indoor air quality due to indoor air pollution is known to affect the health, comfort, and well-being of building occupants. It has also be ...

by diluting and displacing indoor effluents and pollutants. It can also be used to control indoor temperature, humidity, and air motion to benefit

thermal comfort Thermal comfort is the condition of mind that expresses subjective satisfaction with the thermal environment.ANSI/ASHRAE Standard 55-2017, Thermal Environmental Conditions for Human Occupancy The human body can be viewed as a heat engine where ...

, satisfaction with other aspects of the indoor environment, or other objectives. The intentional introduction of outdoor air is usually categorized as either mechanical ventilation,

natural ventilation Passive ventilation is the process of supplying air to and removing air from an indoor space without using mechanical systems. It refers to the flow of external air to an indoor space as a result of pressure differences arising from natural for ...

, or mixed-mode ventilation. * Mechanical ventilation is the intentional fan-driven flow of outdoor air into and/or out from a building. Mechanical ventilation systems may include supply fans (which push outdoor air into a building),

exhaust Exhaust, exhaustive, or exhaustion may refer to: Law * Exhaustion of intellectual property rights, limits to intellectual property rights in patent and copyright law ** Exhaustion doctrine, in patent law ** Exhaustion doctrine under U.S. law, i ...

fans (which draw air out of a building and thereby cause equal ventilation flow into a building), or a combination of both (called balanced ventilation if it neither pressurizes nor depressurizes the inside air,Whole-House Ventilation , Department of Energy
/ref> or only slightly depressurizes it). Mechanical ventilation is often provided by equipment that is also used to heat and cool a space. * Natural ventilation is the intentional passive flow of outdoor air into a building through planned openings (such as louvers, doors, and windows). Natural ventilation does not require mechanical systems to move outdoor air. Instead, it relies entirely on passive physical phenomena, such as wind pressure, or the stack effect. Natural ventilation openings may be fixed, or adjustable. Adjustable openings may be controlled automatically (automated), owned by occupants (operable), or a combination of both.

Cross ventilation Cross ventilation is a natural phenomenon where wind enters an opening, such as a window, flows directly through the space, and exits through an opening on the opposite side of the building (where the air pressure is lower). This produces a cool s ...

is a phenomenon of natural ventilation. * Mixed-mode ventilation systems use both mechanical and natural processes. The mechanical and natural components may be used at the same time, at different times of day, or in different seasons of the year. Since natural ventilation flow depends on environmental conditions, it may not always provide an appropriate amount of ventilation. In this case, mechanical systems may be used to supplement or regulate the naturally driven flow. Ventilation is typically described as separate from infiltration. * Infiltration is the circumstantial flow of air from outdoors to indoors through leaks (unplanned openings) in a

building envelope A building envelope or building enclosure is the physical separator between the conditioned and unconditioned environment of a building, including the resistance to air, water, heat, light, and noiseSyed, Asif. ''Advanced building technologies for ...

. When a building design relies on infiltration to maintain indoor air quality, this flow has been referred to as adventitious ventilation. The design of buildings that promote occupant health and well-being requires a clear understanding of the ways that ventilation airflow interacts with, dilutes, displaces, or introduces pollutants within the occupied space. Although ventilation is an integral component of maintaining good indoor air quality, it may not be satisfactory alone. A clear understanding of both indoor and outdoor air quality parameters is needed to improve the performance of ventilation in terms of occupant health and energy. In scenarios where outdoor

pollution Pollution is the introduction of contaminants into the natural environment that cause harm. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the component ...

would deteriorate indoor air quality, other treatment devices such as

filtration Filtration is a physical separation process that separates solid matter and fluid from a mixture using a ''filter medium'' that has a complex structure through which only the fluid can pass. Solid particles that cannot pass through the filte ...

may also be necessary. In kitchen ventilation systems, or for laboratory fume hoods, the design of effective effluent capture can be more important than the bulk amount of ventilation in a space. More generally, the way that an air distribution system causes ventilation to flow into and out of a space impacts the ability of a particular ventilation rate to remove internally generated pollutants. The ability of a system to reduce pollution in space is described as its "ventilation effectiveness". However, the overall impacts of ventilation on indoor air quality can depend on more complex factors such as the sources of pollution, and the ways that activities and airflow interact to affect occupant exposure. An array of factors related to the design and operation of ventilation systems are regulated by various codes and standards. Standards dealing with the design and operation of ventilation systems to achieve acceptable indoor air quality include the American Society of Heating, Refrigerating and Air-Conditioning Engineers (

ASHRAE The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE ) is an American professional association seeking to advance heating, ventilation, air conditioning and refrigeration (HVAC&R) systems design and constructio ...

) Standards 62.1 and 62.2, the International Residential Code, the International Mechanical Code, and the United Kingdom Building Regulations Part F. Other standards that focus on energy conservation also impact the design and operation of ventilation systems, including ASHRAE Standard 90.1, and the International Energy Conservation Code. When indoor and outdoor conditions are favorable, increasing ventilation beyond the minimum required for indoor air quality can significantly improve both indoor air quality and thermal comfort through

ventilative cooling Ventilative cooling is the use of natural or mechanical ventilation to cool indoor spaces.P. Heiselberg, M. Kolokotroni.Ventilative Cooling. State of the art review. Department of Civil Engineering. Aalborg University, Denmark. 2015 The use of outs ...

, which also helps reduce the energy demand of buildings. During these times, higher ventilation rates, achieved through

passive Passive may refer to: * Passive voice, a grammatical voice common in many languages, see also Pseudopassive * Passive language, a language from which an interpreter works * Passivity (behavior), the condition of submitting to the influence of ...

or mechanical means ( air-side economizer, ventilative pre-cooling), can be particularly beneficial for enhancing people's physical health.Sun, Y., Zhang, Y., Bao, L., Fan, Z. and Sundell, J., 2011. Ventilation and dampness in dorms and their associations with allergy among college students in China: a case-control study. Indoor Air, 21(4), pp.277-283. Conversely, when conditions are less favorable, maintaining or improving indoor air quality through ventilation may require increased use of mechanical heating or cooling, leading to higher energy consumption. Ventilation should be considered for its relationship to "venting" for appliances and combustion equipment such as water heaters, furnaces,

boiler A boiler is a closed vessel in which fluid (generally water) is heated. The fluid does not necessarily boil. The heated or vaporized fluid exits the boiler for use in various processes or heating applications, including water heating, centra ...

s, and wood stoves. Most importantly, building ventilation design must be careful to avoid the backdraft of combustion products from "naturally vented" appliances into the occupied space. This issue is of greater importance for buildings with more air-tight envelopes. To avoid the hazard, many modern combustion appliances utilize "direct venting" which draws combustion air directly from outdoors, instead of from the indoor environment.

Design of air flow in rooms

The air in a room can be supplied and removed in several ways, for example via ceiling ventilation,

cross ventilation Cross ventilation is a natural phenomenon where wind enters an opening, such as a window, flows directly through the space, and exits through an opening on the opposite side of the building (where the air pressure is lower). This produces a cool s ...

, floor ventilation or

displacement ventilation Displacement ventilation (DV) is a room air distribution strategy where conditioned outdoor air is supplied at a low velocity from air supply diffusers located near floor level and extracted above the occupied zone, usually at ceiling height. Sys ...

. Verdrängungslüftung Decke.JPG, Ceiling ventilation Verdrängungslüftung Quer.JPG,

Verdrängungslüftung Boden.JPG, Floor ventilation Verdrängungslüftung Quell.JPG,

Displacement ventilation Displacement ventilation (DV) is a room air distribution strategy where conditioned outdoor air is supplied at a low velocity from air supply diffusers located near floor level and extracted above the occupied zone, usually at ceiling height. Sys ...

Furthermore, the air can be circulated in the room using vortexes which can be initiated in various ways: Verdünnungslüftung horizontal.JPG, Tangential flow vortices, initiated horizontally Verdünnungslüftung vertikal.JPG, Tangential flow vortices, initiated vertically Verdünnungslüftung Strahl.JPG, Diffused flow vortices from air nozzles Verdünnungslüftung Drall.JPG, Diffused flow vortices due to roof vortices

Ventilation rates for indoor air quality

The ventilation rate, for commercial, industrial, and institutional (CII) buildings, is normally expressed by the volumetric flow rate of outdoor air, introduced to the building. The typical units used are

cubic feet per minute The cubic foot (symbol ft3 or cu ft)
, . is an cubic meter per second is the preferred unit for

volumetric flow rate In physics and engineering, in particular fluid dynamics, the volumetric flow rate (also known as volume flow rate, or volume velocity) is the volume of fluid which passes per unit time; usually it is represented by the symbol (sometimes \do ...

in the SI system of units). The ventilation rate can also be expressed on a per person or per unit floor area basis, such as CFM/p or CFM/ft², or as air changes per hour (ACH).

Standards for residential buildings

For residential buildings, which mostly rely on infiltration for meeting their ventilation needs, a common ventilation rate measure is the air change rate (or air changes per hour): the hourly ventilation rate divided by the volume of the space (''I'' or ''ACH''; units of 1/h). During the winter, ACH may range from 0.50 to 0.41 in a tightly air-sealed house to 1.11 to 1.47 in a loosely air-sealed house. ASHRAE now recommends ventilation rates dependent upon floor area, as a revision to the 62-2001 standard, in which the minimum ACH was 0.35, but no less than 15 CFM/person (7.1 L/s/person). As of 2003, the standard has been changed to 3 CFM/100 sq. ft. (15 L/s/100 sq. m.) plus 7.5 CFM/person (3.5 L/s/person).

Standards for commercial buildings

Ventilation rate procedure

Ventilation Rate Procedure is rate based on standard and prescribes the rate at which ventilation air must be delivered to space and various means to the condition that air.ASHRAE Standard 62 Air quality is assessed (through CO₂ measurement) and ventilation rates are mathematically derived using constants.Indoor Air Quality Procedure uses one or more guidelines for the specification of acceptable concentrations of certain contaminants in indoor air but does not prescribe ventilation rates or air treatment methods. This addresses both quantitative and subjective evaluations and is based on the Ventilation Rate Procedure. It also accounts for potential contaminants that may have no measured limits, or for which no limits are not set (such as formaldehyde off-gassing from carpet and furniture).

Natural ventilation

Natural ventilation Passive ventilation is the process of supplying air to and removing air from an indoor space without using mechanical systems. It refers to the flow of external air to an indoor space as a result of pressure differences arising from natural for ...

harnesses naturally available forces to supply and remove air in an enclosed space. Poor ventilation in rooms is identified to significantly increase the localized moldy smell in specific places of the room including room corners. There are three types of natural ventilation occurring in buildings: wind-driven ventilation, pressure-driven flows, and

stack ventilation Stack may refer to: Places * Stack Island, an island game reserve in Bass Strait, south-eastern Australia, in Tasmania’s Hunter Island Group * Blue Stack Mountains, in Co. Donegal, Ireland People * Stack (surname) (including a list of people ...

. The pressures generated by 'the stack effect' rely upon the buoyancy of heated or rising air. Wind-driven ventilation relies upon the force of the prevailing wind to pull and push air through the enclosed space as well as through breaches in the building's envelope. Almost all historic buildings were ventilated naturally. The technique was generally abandoned in larger US buildings during the late 20th century as the use of air conditioning became more widespread. However, with the advent of advanced Building Performance Simulation (BPS) software, improved

Building Automation Building automation (BAS), also known as building management system (BMS) or building energy management system (BEMS), is the automatic centralized control of a building's HVAC, HVAC (heating, ventilation and air conditioning), electrical, light ...

Systems (BAS),

Leadership in Energy and Environmental Design Leadership in Energy and Environmental Design (LEED) is a Green building certification systems, green building certification program used worldwide. Developed by the non-profit U.S. Green Building Council (USGBC), it includes a set of rating ...

(LEED) design requirements, and improved window manufacturing techniques; natural ventilation has made a resurgence in commercial buildings both globally and throughout the US. The benefits of natural ventilation include: *Improved

(IAQ) *Energy savings *Reduction of

greenhouse gas emissions Greenhouse gas (GHG) emissions from human activities intensify the greenhouse effect. This contributes to climate change. Carbon dioxide (), from burning fossil fuels such as coal, petroleum, oil, and natural gas, is the main cause of climate chan ...

*Occupant control *Reduction in occupant illness associated with

sick building syndrome Sick building syndrome (SBS) is a condition in which people develop symptoms of illness or become infected with chronic disease from the building in which they work or reside. In scientific literature, SBS is also known as building-related illn ...

*Increased worker productivity Techniques and architectural features used to ventilate buildings and structures naturally include, but are not limited to: *Operable windows *Clerestory windows and vented skylights * Lev/convection doors *Night purge ventilation *Building orientation *Wind capture façades

Airborne diseases

Natural ventilation is a key factor in reducing the spread of airborne illnesses such as tuberculosis, the common cold, influenza, meningitis or COVID-19. Opening doors and windows are good ways to maximize natural ventilation, which would make the risk of airborne contagion much lower than with costly and maintenance-requiring mechanical systems. Old-fashioned clinical areas with high ceilings and large windows provide the greatest protection. Natural ventilation costs little and is maintenance-free, and is particularly suited to limited-resource settings and tropical climates, where the burden of TB and institutional TB transmission is highest. In settings where respiratory isolation is difficult and climate permits, windows and doors should be opened to reduce the risk of airborne contagion. Natural ventilation requires little maintenance and is inexpensive. Natural ventilation is not practical in much of the infrastructure because of climate. This means that the facilities need to have effective mechanical ventilation systems and or use Ceiling Level UV or FAR UV ventilation systems. Ventilation is measured in terms of air changes per hour (ACH). , the CDC recommends that all spaces have a minimum of 5 ACH. For hospital rooms with airborne contagions the CDC recommends a minimum of 12 ACH. Challenges in facility ventilation are public unawareness, ineffective government oversight, poor building codes that are based on comfort levels, poor system operations, poor maintenance, and lack of transparency. Pressure, both political and economic, to improve energy conservation has led to decreased ventilation rates.

Heating, ventilation, and air conditioning Heating, ventilation, and air conditioning (HVAC ) is the use of various technologies to control the temperature, humidity, and purity of the air in an enclosed space. Its goal is to provide thermal comfort and acceptable indoor air quality. H ...

rates have dropped since the

energy crisis An energy crisis or energy shortage is any significant Bottleneck (production), bottleneck in the supply of energy resources to an economy. In literature, it often refers to one of the energy sources used at a certain time and place, in particu ...

in the 1970s and the banning of cigarette smoke in the 1980s and 1990s.

Mechanical ventilation

Mechanical ventilation of buildings and structures can be achieved by the use of the following techniques: *Whole-house ventilation *Mixing ventilation *Displacement ventilation *Dedicated subaerial air supply

Demand-controlled ventilation (DCV)

Demand-controlled ventilation (DCV, also known as Demand Control Ventilation) makes it possible to maintain air quality while conserving energy. ASHRAE has determined that "It is consistent with the ventilation rate procedure that demand control be permitted for use to reduce the total outdoor air supply during periods of less occupancy." In a DCV system, CO₂ sensors control the amount of ventilation. During peak occupancy, CO₂ levels rise, and the system adjusts to deliver the same amount of outdoor air as would be used by the ventilation-rate procedure. However, when spaces are less occupied, CO₂ levels reduce, and the system reduces ventilation to conserves energy. DCV is a well-established practice, and is required in high occupancy spaces by building energy standards such as ASHRAE 90.1.

Personalized ventilation

Personalized ventilation is an air distribution strategy that allows individuals to control the amount of ventilation received. The approach delivers fresh air more directly to the breathing zone and aims to improve the air quality of inhaled air. Personalized ventilation provides much higher ventilation effectiveness than conventional mixing ventilation systems by displacing pollution from the breathing zone with far less air volume. Beyond improved air quality benefits, the strategy can also improve occupants' thermal comfort, perceived air quality, and overall satisfaction with the indoor environment. Individuals' preferences for temperature and air movement are not equal, and so traditional approaches to homogeneous environmental control have failed to achieve high occupant satisfaction. Techniques such as personalized ventilation facilitate control of a more diverse thermal environment that can improve thermal satisfaction for most occupants.

Local exhaust ventilation

Local exhaust ventilation addresses the issue of avoiding the contamination of indoor air by specific high-emission sources by capturing airborne contaminants before they are spread into the environment. This can include water vapor control, lavatory effluent control, solvent vapors from industrial processes, and dust from wood- and metal-working machinery. Air can be exhausted through pressurized hoods or the use of fans and pressurizing a specific area.
A local exhaust system is composed of five basic parts: # A hood that captures the contaminant at its source # Ducts for transporting the air # An air-cleaning device that removes/minimizes the contaminant # A fan that moves the air through the system # An exhaust stack through which the contaminated air is discharged In the UK, the use of LEV systems has regulations set out by the

Health and Safety Executive The Health and Safety Executive (HSE) is a British public body responsible for the encouragement, regulation and enforcement of workplace health, safety and welfare. It has additionally adopted a research role into occupational risks in Great B ...

(HSE) which are referred to as the Control of Substances Hazardous to Health ( CoSHH). Under CoSHH, legislation is set to protect users of LEV systems by ensuring that all equipment is tested at least every fourteen months to ensure the LEV systems are performing adequately. All parts of the system must be visually inspected and thoroughly tested and where any parts are found to be defective, the inspector must issue a red label to identify the defective part and the issue. The owner of the LEV system must then have the defective parts repaired or replaced before the system can be used.

Smart ventilation

Smart ventilation is a process of continually adjusting the ventilation system in time, and optionally by location, to provide the desired IAQ benefits while minimizing energy consumption, utility bills, and other non-IAQ costs (such as thermal discomfort or noise). A smart ventilation system adjusts ventilation rates in time or by location in a building to be responsive to one or more of the following: occupancy, outdoor thermal and air quality conditions, electricity grid needs, direct sensing of contaminants, operation of other air moving and air cleaning systems. In addition, smart ventilation systems can provide information to building owners, occupants, and managers on operational energy consumption and indoor air quality as well as a signal when systems need maintenance or repair. Being responsive to occupancy means that a smart ventilation system can adjust ventilation depending on demand such as reducing ventilation if the building is unoccupied. Smart ventilation can time-shift ventilation to periods when a) indoor-outdoor temperature differences are smaller (and away from peak outdoor temperatures and humidity), b) when indoor-outdoor temperatures are appropriate for ventilative cooling, or c) when outdoor air quality is acceptable. Being responsive to electricity grid needs means providing flexibility to electricity demand (including direct signals from utilities) and integration with electric grid control strategies. Smart ventilation systems can have sensors to detect airflow, systems pressures, or fan energy use in such a way that systems failures can be detected and repaired, as well as when system components need maintenance, such as filter replacement.

Ventilation and combustion

Combustion Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combustion ...

(in a fireplace, gas heater,

candle A candle is an ignitable candle wick, wick embedded in wax, or another flammable solid substance such as tallow, that provides light, and in some cases, a Aroma compound, fragrance. A candle can also provide heat or a method of keeping time. ...

oil lamp An oil lamp is a lamp used to produce light continuously for a period of time using an oil-based fuel source. The use of oil lamps began thousands of years ago and continues to this day, although their use is less common in modern times. The ...

, etc.) consumes oxygen while producing carbon dioxide and other unhealthy gases and

smoke Smoke is an aerosol (a suspension of airborne particulates and gases) emitted when a material undergoes combustion or pyrolysis, together with the quantity of air that is entrained or otherwise mixed into the mass. It is commonly an unwante ...

, requiring ventilation air. An open

chimney A chimney is an architectural ventilation structure made of masonry, clay or metal that isolates hot toxic exhaust gases or smoke produced by a boiler, stove, furnace, incinerator, or fireplace from human living areas. Chimneys are typical ...

promotes infiltration (i.e. natural ventilation) because of the negative pressure change induced by the buoyant, warmer air leaving through the chimney. The warm air is typically replaced by heavier, cold air. Ventilation in a structure is also needed for removing

water vapor Water vapor, water vapour, or aqueous vapor is the gaseous phase of Properties of water, water. It is one Phase (matter), state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from th ...

produced by respiration, burning, and

cooking Cooking, also known as cookery or professionally as the culinary arts, is the art, science and craft of using heat to make food more palatable, digestible, nutritious, or Food safety, safe. Cooking techniques and ingredients vary widely, from ...

, and for removing odors. If water vapor is permitted to accumulate, it may damage the structure, insulation, or finishes. When operating, an air conditioner usually removes excess moisture from the air. A

dehumidifier A dehumidifier is an air conditioning device which reduces and maintains the level of humidity in the air. This is done usually for health or thermal comfort reasons or to eliminate musty odor and to prevent the growth of mildew by extracting wate ...

may also be appropriate for removing airborne moisture.

Calculation for acceptable ventilation rate

Ventilation guidelines are based on the minimum ventilation rate required to maintain acceptable levels of effluents. Carbon dioxide is used as a reference point, as it is the gas of highest emission at a relatively constant value of 0.005 L/s. The mass balance equation is: Q = G/ (C_i − C_a) *Q = ventilation rate (L/s) *G = CO₂ generation rate *C_i = acceptable indoor CO₂ concentration *C_a = ambient CO₂ concentration

Smoking and ventilation

ASHRAE standard 62 states that air removed from an area with environmental tobacco smoke shall not be recirculated into ETS-free air. A space with ETS requires more ventilation to achieve similar perceived air quality to that of a non-smoking environment. The amount of ventilation in an ETS area is equal to the amount of an ETS-free area plus the amount V, where: V = DSD × VA × A/60E *V = recommended extra flow rate in CFM (L/s) *DSD = design smoking density (estimated number of cigarettes smoked per hour per unit area) *VA = volume of ventilation air per cigarette for the room being designed (ft³/cig) *E = contaminant removal effectivenessASHRAE, Ventilation for Acceptable Indoor Air Quality. American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc, Atlanta, 2002.

History

Primitive ventilation systems were found at the Pločnik archeological site (belonging to the Vinča culture) in Serbia and were built into early copper smelting furnaces. The furnace, built on the outside of the workshop, featured earthen pipe-like air vents with hundreds of tiny holes in them and a prototype chimney to ensure air goes into the furnace to feed the fire and smoke comes out safely. Passive ventilation and passive cooling systems were widely written about around the Mediterranean by Classical times. Both sources of heat and sources of cooling (such as fountains and subterranean heat reservoirs) were used to drive air circulation, and buildings were designed to encourage or exclude drafts, according to climate and function. Public bathhouses were often particularly sophisticated in their heating and cooling. Icehouses are some millennia old, and were part of a well-developed ice industry by classical times. The development of forced ventilation was spurred by the common belief in the late 18th and early 19th century in the miasma theory of

disease A disease is a particular abnormal condition that adversely affects the structure or function (biology), function of all or part of an organism and is not immediately due to any external injury. Diseases are often known to be medical condi ...

, where stagnant 'airs' were thought to spread illness. An early method of ventilation was the use of a ventilating fire near an air vent which would forcibly cause the air in the building to circulate. English engineer

John Theophilus Desaguliers John Theophilus Desaguliers (12 March 1683 – 29 February 1744) was a French-born British natural philosopher, clergyman, engineer and freemason who was elected to the Royal Society in 1714 as experimental assistant to Isaac Newton. He had stu ...

provided an early example of this when he installed ventilating fires in the air tubes on the roof of the

House of Commons The House of Commons is the name for the elected lower house of the Bicameralism, bicameral parliaments of the United Kingdom and Canada. In both of these countries, the Commons holds much more legislative power than the nominally upper house of ...

. Starting with the Covent Garden Theatre, gas burning

chandelier A chandelier () is an ornamental lighting device, typically with spreading branched supports for multiple lights, designed to be hung from the ceiling. Chandeliers are often ornate, and they were originally designed to hold candles, but now inca ...

s on the ceiling were often specially designed to perform a ventilating role.

Mechanical systems

A more sophisticated system involving the use of mechanical equipment to circulate the air was developed in the mid-19th century. A basic system of

bellows A bellows or pair of bellows is a device constructed to furnish a strong blast of air. The simplest type consists of a flexible bag comprising a pair of rigid boards with handles joined by flexible leather sides enclosing an approximately airtig ...

was put in place to ventilate

Newgate Prison Newgate Prison was a prison at the corner of Newgate Street and Old Bailey, just inside the City of London, England, originally at the site of Newgate, a gate in the Roman London Wall. Built in the 12th century and demolished in 1904, the pr ...

and outlying buildings, by the engineer

Stephen Hales Stephen Hales (17 September 16774 January 1761) was an English clergyman who made major contributions to a range of scientific fields including botany, pneumatic chemistry and physiology. He was the first person to measure blood pressure. He al ...

in the mid-1700s. The problem with these early devices was that they required constant human labor to operate. David Boswell Reid was called to testify before a Parliamentary committee on proposed architectural designs for the new

, after the old one burned down in a fire in 1834. In January 1840 Reid was appointed by the committee for the

House of Lords The House of Lords is the upper house of the Parliament of the United Kingdom. Like the lower house, the House of Commons of the United Kingdom, House of Commons, it meets in the Palace of Westminster in London, England. One of the oldest ext ...

dealing with the construction of the replacement for the Houses of Parliament. The post was in the capacity of ventilation engineer, in effect; and with its creation there began a long series of quarrels between Reid and

Charles Barry Sir Charles Barry (23 May 1795 – 12 May 1860) was an English architect best known for his role in the rebuilding of the Palace of Westminster (also known as the Houses of Parliament) in London during the mid-19th century, but also responsi ...

, the architect. Reid advocated the installation of a very advanced ventilation system in the new House. His design had air being drawn into an underground chamber, where it would undergo either heating or cooling. It would then ascend into the chamber through thousands of small holes drilled into the floor, and would be extracted through the ceiling by a special ventilation fire within a great stack. Reid's reputation was made by his work in Westminster. He was commissioned for an

air quality Air pollution is the presence of substances in the Atmosphere of Earth, air that are harmful to humans, other living beings or the environment. Pollutants can be Gas, gases like Ground-level ozone, ozone or nitrogen oxides or small particles li ...

survey in 1837 by the Leeds and Selby Railway in their tunnel. The steam vessels built for the Niger expedition of 1841 were fitted with ventilation systems based on Reid's Westminster model. Air was dried, filtered and passed over charcoal. Reid's ventilation method was also applied more fully to St. George's Hall, Liverpool, where the architect, Harvey Lonsdale Elmes, requested that Reid should be involved in ventilation design. Reid considered this the only building in which his system was completely carried out.

Fans

With the advent of practical steam power, ceiling fans could finally be used for ventilation. Reid installed four steam-powered fans in the ceiling of St George's Hospital in

Liverpool Liverpool is a port City status in the United Kingdom, city and metropolitan borough in Merseyside, England. It is situated on the eastern side of the River Mersey, Mersey Estuary, near the Irish Sea, north-west of London. With a population ...

, so that the pressure produced by the fans would force the incoming air upward and through vents in the ceiling. Reid's pioneering work provides the basis for ventilation systems to this day. He was remembered as "Dr. Reid the ventilator" in the twenty-first century in discussions of energy efficiency, by Lord Wade of Chorlton.

History and development of ventilation rate standards

Ventilating a space with fresh air aims to avoid "bad air". The study of what constitutes bad air dates back to the 1600s when the scientist Mayow studied

asphyxia Asphyxia or asphyxiation is a condition of deficient supply of oxygen to the body which arises from abnormal breathing. Asphyxia causes generalized hypoxia, which affects all the tissues and organs, some more rapidly than others. There are m ...

of animals in confined bottles. The poisonous component of air was later identified as carbon dioxide (), by Lavoisier in the very late 1700s, starting a debate as to the nature of "bad air" which humans perceive to be stuffy or unpleasant. Early hypotheses included excess concentrations of and oxygen depletion. However, by the late 1800s, scientists thought biological contamination, not oxygen or , was the primary component of unacceptable indoor air. However, it was noted as early as 1872 that concentration closely correlates to perceived air quality. The first estimate of minimum ventilation rates was developed by Tredgold in 1836. This was followed by subsequent studies on the topic by Billings in 1886 and Flugge in 1905. The recommendations of Billings and Flugge were incorporated into numerous building codes from 1900–the 1920s and published as an industry standard by ASHVE (the predecessor to

) in 1914. The study continued into the varied effects of

, oxygen, carbon dioxide, and biological contaminants. The research was conducted with human subjects in controlled test chambers. Two studies, published between 1909 and 1911, showed that carbon dioxide was not the offending component. Subjects remained satisfied in chambers with high levels of , so long as the chamber remained cool. (Subsequently, it has been determined that is, in fact, harmful at concentrations over 50,000ppm) ASHVE began a robust research effort in 1919. By 1935, ASHVE-funded research conducted by Lemberg, Brandt, and Morse – again using human subjects in test chambers – suggested the primary component of "bad air" was an odor, perceived by the human olfactory nerves. Human response to odor was found to be logarithmic to contaminant concentrations, and related to temperature. At lower, more comfortable temperatures, lower ventilation rates were satisfactory. A 1936 human test chamber study by Yaglou, Riley, and Coggins culminated much of this effort, considering odor, room volume, occupant age, cooling equipment effects, and recirculated air implications, which guided ventilation rates. The Yagle research has been validated, and adopted into industry standards, beginning with the ASA code in 1946. From this research base,

(having replaced ASHVE) developed space-by-space recommendations, and published them as ASHRAE Standard 62-1975: Ventilation for acceptable indoor air quality. As more architecture incorporated mechanical ventilation, the cost of outdoor air ventilation came under some scrutiny. In 1973, in response to the

1973 oil crisis In October 1973, the Organization of Arab Petroleum Exporting Countries (OAPEC) announced that it was implementing a total oil embargo against countries that had supported Israel at any point during the 1973 Yom Kippur War, which began after Eg ...

and conservation concerns, ASHRAE Standards 62-73 and 62–81) reduced required ventilation from 10 CFM (4.76 L/s) per person to 5 CFM (2.37 L/s) per person. In cold, warm, humid, or dusty climates, it is preferable to minimize ventilation with outdoor air to conserve energy, cost, or filtration. This critique (e.g. Tiller) led ASHRAE to reduce outdoor ventilation rates in 1981, particularly in non-smoking areas. However subsequent research by Fanger, W. Cain, and Janssen validated the Yagle model. The reduced ventilation rates were found to be a contributing factor to

. The 1989 ASHRAE standard (Standard 62–89) states that appropriate ventilation guidelines are 20 CFM (9.2 L/s) per person in an office building, and 15 CFM (7.1 L/s) per person for schools, while 2004 Standard 62.1-2004 has lower recommendations again (see tables below). ANSI/ASHRAE (Standard 62–89) speculated that "comfort (odor) criteria are likely to be satisfied if the ventilation rate is set so that 1,000 ppm CO₂ is not exceeded" while OSHA has set a limit of 5000 ppm over 8 hours. ASHRAE continues to publish space-by-space ventilation rate recommendations, which are decided by a consensus committee of industry experts. The modern descendants of ASHRAE standard 62-1975 are ASHRAE Standard 62.1, for non-residential spaces, and ASHRAE 62.2 for residences. In 2004, the calculation method was revised to include both an occupant-based contamination component and an area–based contamination component.Stanke D. 2006. "Explaining Science Behind Standard 62.1-2004". ASHRAE IAQ Applications, V7, Summer 2006. accessed 11 June 2014 These two components are additive, to arrive at an overall ventilation rate. The change was made to recognize that densely populated areas were sometimes overventilated (leading to higher energy and cost) using a per-person methodology. Occupant Based Ventilation Rates, ANSI/ASHRAE Standard 62.1-2004 Area-based ventilation rates, ANSI/ASHRAE Standard 62.1-2004 The addition of occupant- and area-based ventilation rates found in the tables above often results in significantly reduced rates compared to the former standard. This is compensated in other sections of the standard which require that this minimum amount of air is delivered to the breathing zone of the individual occupant at all times. The total outdoor air intake of the ventilation system (in multiple-zone variable air volume (VAV) systems) might therefore be similar to the airflow required by the 1989 standard.
From 1999 to 2010, there was considerable development of the application protocol for ventilation rates. These advancements address occupant- and process-based ventilation rates, room ventilation effectiveness, and system ventilation effectiveness

Problems

* In hot, humid climates, unconditioned ventilation air can daily deliver approximately 260

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s of water for each cubic meters per hour (m³/h) of outdoor air (or one pound of water each day for each cubic feet per minute of outdoor air per day), annual average. This is a great deal of moisture and can create serious indoor moisture and

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problems. For example, given a 150 m² building with an airflow of 180 m³/h this could result in about 47 liters of water accumulated per day. * Ventilation efficiency is determined by design and layout, and is dependent upon the placement and proximity of diffusers and return air outlets. If they are located closely together, supply air may mix with stale air, decreasing the efficiency of the HVAC system, and creating air quality problems. * System imbalances occur when components of the HVAC system are improperly adjusted or installed and can create pressure differences (too much-circulating air creating a draft or too little circulating air creating stagnancy). * Cross-contamination occurs when pressure differences arise, forcing potentially contaminated air from one zone to an uncontaminated zone. This often involves undesired odors or VOCs. * Re-entry of exhaust air occurs when exhaust outlets and fresh air intakes are either too close, prevailing winds change exhaust patterns or infiltration between intake and exhaust air flows. * Entrainment of contaminated outdoor air through intake flows will result in indoor air contamination. There are a variety of contaminated air sources, ranging from industrial effluent to VOCs put off by nearby construction work. A recent study revealed that in urban European buildings equipped with ventilation systems lacking outdoor air filtration, the exposure to outdoor-originating pollutants indoors resulted in more Disability-Adjusted Life Years ( DALYs) than exposure to indoor-emitted pollutants.

References

External links

Air Infiltration & Ventilation Centre (AIVC)

Publications
from the Air Infiltration & Ventilation Centre (AIVC)

International Energy Agency (IEA) Energy in Buildings and Communities Programme (EBC)

*Publications from the International Energy Agency (IEA) Energy in Buildings and Communities Programme (EBC) ventilation-related research projects-annexes:
EBC Annex 9 Minimum Ventilation Rates

EBC Annex 18 Demand Controlled Ventilation Systems

EBC Annex 26 Energy Efficient Ventilation of Large Enclosures

EBC Annex 27 Evaluation and Demonstration of Domestic Ventilation Systems

EBC Annex 35 Control Strategies for Hybrid Ventilation in New and Retrofitted Office Buildings (HYBVENT)

EBC Annex 62 Ventilative Cooling

International Society of Indoor Air Quality and Climate

Indoor Air Journal
* Indoor Air Conference Proceedings

American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE)

ASHRAE Standard 62.1 – Ventilation for Acceptable Indoor Air Quality

ASHRAE Standard 62.2 – Ventilation for Acceptable Indoor Air Quality in Residential Buildings
{{Authority control Heating, ventilation, and air conditioning Building biology Fluid dynamics Indoor air pollution