A centimetre or millimetre of water (US spelling ''centimeter'' or ''millimeter of water'') are less commonly used measures of

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and eve ...

based on the

pressure head In fluid mechanics, pressure head is the height of a liquid column that corresponds to a particular pressure exerted by the liquid column on the base of its container. It may also be called static pressure head or simply static head (but not ''sta ...

of water.

Centimetre of water

A ''centimetre of water''NOTE: A centimetre of water is abbreviated as ''cm'' or ''cm H₂O''. is a unit of pressure. It may be defined as the pressure exerted by a column of

water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...

of 1 cm in

height Height is measure of vertical distance, either vertical extent (how "tall" something or someone is) or vertical position (how "high" a point is). For an example of vertical extent, "This basketball player is 7 foot 1 inches in height." For an e ...

at 4 °C (temperature of maximum density) at the standard acceleration of gravity, so that = × × 1 cm = ≈ , but conventionally a nominal maximum water density of is used, giving . The centimetre of water unit is frequently used to measure the central venous pressure, the

intracranial pressure Intracranial pressure (ICP) is the pressure exerted by fluids such as cerebrospinal fluid (CSF) inside the skull and on the brain tissue. ICP is measured in millimeters of mercury ( mmHg) and at rest, is normally 7–15 mmHg for a supine adu ...

while sampling

cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless Extracellular fluid#Transcellular fluid, transcellular body fluid found within the meninges, meningeal tissue that surrounds the vertebrate brain and spinal cord, and in the ventricular system, ven ...

, as well as determining pressures during

mechanical ventilation Mechanical ventilation or assisted ventilation is the Medicine, medical term for using a ventilator, ventilator machine to fully or partially provide artificial ventilation. Mechanical ventilation helps move air into and out of the lungs, wit ...

or in

water supply network A water supply network or water supply system is a system of engineered hydrologic and hydraulic components that provide water supply. A water supply system typically includes the following: # A drainage basin (see water purification – sour ...

s (then usually in

metre The metre (or meter in US spelling; symbol: m) is the base unit of length in the International System of Units (SI). Since 2019, the metre has been defined as the length of the path travelled by light in vacuum during a time interval of of ...

s water column). It is also a common unit of pressure in the speech sciences. This unit is commonly used to specify the pressure to which a CPAP machine is set after a polysomnogram. :

Millimetre of water

''Millimetre of water'' (US spelling ''millimeter of water'')NOTE: Millimetre of water is also sometimes addressed as : ''millimetres water column'', abbreviated as ''mmwg'', ''mmH₂O'', or ''mmwc''. is a unit of pressure. It may be defined as the pressure exerted by a column of

of 1 mm in

at 4 °C (temperature of maximum density) at the standard acceleration of gravity, so that = × × 1 mm = ≈ , but conventionally a nominal maximum water density of is used, giving . : In limited and largely historic contexts it may vary with

temperature Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measurement, measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making ...

, using the equation: : ''P'' = ''ρ''·''g''·''h''/1000, : where : ''P'': pressure in Pa : ''ρ'': density of water (conventionally 1000 kg/m³ at 4 °C) : ''g'': acceleration due to gravity (conventionally 9.80665 m/s² but sometimes locally determined) : ''h'': water height in millimetres. The unit is often used to describe how much water rainwear or other

outerwear Outerwear is clothing and accessories worn outdoors, or clothing designed to be worn as protective layers outside other garments, as opposed to underwear. It can be worn for formal or casual occasions, or as warm clothing during winter. List of ou ...

can take or how much water a

tent A tent is a shelter consisting of sheets of fabric or other material draped over or attached to a frame of poles or a supporting rope. While smaller tents may be free-standing or attached to the ground, large tents are usually anchored using g ...

can resist without leaking.

References

{{reflist

External links

Pressure conversion calculator
at

Cornell University Cornell University is a Private university, private Ivy League research university based in Ithaca, New York, United States. The university was co-founded by American philanthropist Ezra Cornell and historian and educator Andrew Dickson W ...

website Units of pressure

Centimetre of water

Millimetre of water

See also

References

External links