ventilation

n.

1. 1. The replacement of stale or noxious air with fresh air.
   2. The mechanical system or equipment used to circulate air or to replace stale air with fresh air.
2. See respiration (sense ).
3. Aeration or oxygenation, as of blood.

The supplying of air motion in a space by circulation or by moving air through the space. Ventilation may be produced by any combination of natural or mechanical supply and exhaust. Such systems may include partial treatment such as heating, humidity control, filtering or purification, and, in some cases, evaporative cooling. More complete treatment of the air is generally called air conditioning. See also Air conditioning.

Natural ventilation may be provided by wind force, convection, or a combination of the two. Although largely supplanted by mechanical ventilation and air conditioning, natural ventilation still is widely used in homes, schools, and commercial and industrial buildings.

Mechanical supply ventilation may be of the central type consisting of a central fan system with distributing ducts serving a large space or a number of spaces, or of the unitary type with little or no ductwork, serving a single space or a portion of large space. Outside air connections are generally provided for all ducted systems. Outside air is needed in controlled quantities to remove odors and to replace air exhausted from the various building spaces and equipment.

Exhaust ventilation is required to remove odors, fumes, dust, and heat from an enclosed occupied space. Such exhaust may be of the natural variety or may be mechanical by means of roof or wall exhaust fans or mechanical exhaust systems. The mechanical systems may have minimal ductwork or none at all, or may be provided with extensive ductwork which is used to collect localized hot air, gases, fumes, or dust from process operations. Where it is possible to do so, the process operations are enclosed or hooded to provide maximum collection efficiency with the minimum requirement of exhaust air.

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Ventilation in the physiological sense (strictly, pulmonary ventilation) refers to the volume of air breathed in and out of the lungs: typically 5-6 litres per minute for an average-sized person at rest, with the possibility of increasing by up to twenty-fold in exercise. For example, the size of each breath (tidal volume) could vary from 0.5 to 3 litres, and the number of breaths per minute from 10 to 40. When for any reason breathing stops or becomes inadequate, or if natural breathing is prevented by drug-induced muscle relaxation as an adjunct to anaesthesia, mechanical or artificial ventilation (also known as artificial respiration) is necessary. Methods range from mouth-to-mouth breathing to machines which pump gas rhythmically into the lungs

— Stuart Judge

See breathing; breathing during exercise.

noun

An exchanging of views: conference, discussion. Slang rap³. See words.

v

1. to provide with fresh air. v 2. to provide the lungs with air from the atmosphere. v 3. to open, to free, as in to openly express one’s feelings.

The process of supplying or removing air, by natural or mechanical means, to or from any space; such air may or may not have been conditioned.

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The passage of air into and out of the lungs. See also alveolar ventilation, pulmonary ventilation.

Renewal or exchange of gas in an enclosed space.
1. the process or act of supplying a building or part of it continuously with fresh air.
2. in respiratory physiology, the process of exchange of air between the lungs and the ambient air. Pulmonary ventilation (usually measured in liters per minute) refers to the total exchange, whereas alveolar ventilation refers to the effective ventilation of the alveoli, where gas exchange with the blood takes place. See also air movement.

• alveolar v. — the amount of gas expelled from the alveoli to the outside of the body per minute.
• artificial v. — see artificial respiration.
• assisted v. — the depth of spontaneous ventilation is augmented by the anesthetist, as by squeezing the rebreathing bag.
• controlled v. — breathing is done entirely by a mechanical device or the anesthetist squeezing the rebreathing bag.
• dead space v. — see dead space.
• high frequency v. — mechanical ventilation that delivers gas at more than four times the normal rate of breathing.
• intermittent mandatory v. (IMV) — a type of mechanical ventilation in which the ventilator is set to deliver a prescribed tidal volume at specified intervals and a high-flow gas system permits the patient to breathe spontaneously between cycles. The ventilator rate is set to maintain the patient's P_aco₂ at normal levels and is reduced gradually to zero as the patient's condition improves.
• intermittent positive-pressure v. (IPPV) — the provision of mechanical ventilation by a machine designed to deliver breathing gas until equilibrium is established between the patient's lungs and the ventilator. IPPV machines are positive-pressure, pressure-cycled, assister-controller (pneumatic) devices.
— Because of their compact size and capability of operating independently of an electrical current, the IPPV machines have the most widespread applicability in the employment of a form of treatment called intermittent positive-pressure breathing.
• maximal voluntary v. (MVV) — the maximal volume that can be exhaled per minute by the patient breathing as rapidly and deeply as possible.
• mechanical v. — that accomplished by extrinsic means.
• minute v. — the total amount of gas (in liters) expelled from the lungs per minute.
• v. mismatch — mismatches of ventilation and blood flow, as in chronic obstructive lung disease, are a common cause of hypoxemia.
• v.:perfusion ratio — the ratio of air ventilation to the blood perfused. Called also V_A/Q. The degree of oxygenation of the blood and the proportional excretion of CO₂ are both dependent on both variables being optimal.
• positive pressure v. — administration of oxygen under pressure, usually by use of an anesthetic bag or mechanical ventilator. See also continuous positive airway pressure, positive end-expiratory pressure.
• spontaneous v. — breathing without the assistance of any ventilator or mechanical device.
• total v. — the amount of air moved out of (or into) the airways and alveoli over a specified time period.

Encouraging a healthy flow of fresh air in a closed boat
The flow of air inside a boat at anchor is usually from aft forward, especially if you have an open forehatch hinged along its forward edge. Air tends to enter through the main companionway hatch and exit through the fore-hatch. The airflow is maintained when the outside wind is coming from many other directions as well.If you’re adding fans or ventilators, aim to reinforce this natural air circulation, not fight it. Good ventilation is an important part of keeping a boat’s interior dry and sweet, but it’s often badly neglected by manufacturers of production boats.Dorade boxes with cowls facing the prevailing wind, combined with louvered hatch slides for air to escape from, will keep a copious amount of air flowing through a closed boat and discourage the growth of mildew and mold in summer and winter.You should be able to close off ventilators for sea work, of course, but at anchor or in port,

Air flow through a hull

be generous with the size of your ventilator cowls. Perhaps you remember from math class that a 4-inch-diameter cowl provides almost twice as much fresh air as one with a 3-inch diameter—a wonderful bonus for such a modest increase in size.

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