O²:  Oxygen.

OA:   Outdoor air.

Oakum: Loose hemp or jute fiber that is impregnated with tar or pitch and used to caulk large seams or for packing plumbing pipe joints.

Objectives (see Water Quality Objectives):  Ocean Plan  – Limits waste discharge into the ocean. Adopted by the State Water Board in 1972.

Obstruction: (in daylight calculations) Anything outside a building which prevents the direct view of part of the sky.

Occupational Exposure Limit (OEL):  The maximum concentration of an airborne contaminant to which workers may be exposed.

Occupied Zone:   The region within an occupied space between planes 3 and 72 in. (75 and 1800 mm) above the floor and more than 2 ft (600mm) from the walls or fixed air-conditioning equipment.

Ocean Energy:  Waves, tides, differential heat layers, and other sources of energy directly related to the world’s oceans.

Ocean Waters:  Territorial marine waters of the state to the extent that these waters are outside of enclosed bays, estuaries, and coastal lagoons.

Octave Bands: Ranges of frequencies. These octave bands are identified by their center frequencies (63, 125, 250, etc.).

O.D.:  A measurement. Outside diameter.

Odor:   A quality of gases, liquids, or particles that stimulates the olfactory organ or sense of smell.
 
Odor Character or Quality:   The property of the odor sensation that permits a person to distinguish odors of different substances based on prior exposure.
 
Odor Descriptor:   Adjective given to an odor such as “floral,” “caramel,” “putrid.”
 
Odor Pervasiveness:   The rate of decrease of odor perception associated with the decrease in odorant concentration.
 
Odor Threshold:   Concentration of odorous air at which half of the judges in a panel detect the odor.
 
Odorant:   A substance that stimulates the olfactory receptors.

Odorimetry:   Measurement of olfactory sensations.

Odour Threshold:  The minimum concentration of a chemical in the air that someone can detect by sense of smell; it is expressed in ppm.

OECD – Organisation for Economic Co-operation and Development:  The Organization for Economic Co-operation and Development (OECD) is made up of a group of 29 member countries sharing a commitment to democratic government and the market economy. Its work covers economic and social issues, produces internationally agreed-upon instruments, decisions and recommendations that allow for rules where multilateral agreements are necessary for individual countries to make progress in a globalized economy. In the area of safety/toxicity testing of products, the OECD guidelines set standards for such testing, including when animals are used.

OEL:  See Occupational Exposure Limit.

OEM:  Original equipment manufacturer.

Office of Administrative Law (OAL):  A State agency charged with administering the Administrative Procedures Act, reviewing and approving regulations for other State agencies, which once approved, are codified in the California Code of Regulations.

Office of Environmental Health Hazard Assessment (OEHHA): A department within the California Environmental Protection Agency that is responsible for evaluating chemicals for adverse health impacts and establishing safe exposure levels. OEHHA also assists in performing health risk assessments and developing risk assessment procedures for air quality management purposes.

Offset: A method used in the 1990 Clean Air Act to give companies which own or operate large (major) source in a non-attainment area flexibility in meeting overall pollution reduction requirements when changing production processes. If the owner or operator of the source wishes to increase release of a criteria air pollutant, an offset (reduction of a somewhat greater amount of the same pollutant) must be obtained either at the same plant or by purchasing offsets from another company.

Off Gas:  Air or vapor given off or expelled as a byproduct or result of an operation or treatment process.

Off-Gassing: The production of gases from the chemical deterioration of a substance over time.

Off Site:  Outside the boundaries of the LLNL Livermore site or Site 300 properties.

O. G. (or Ogee): A molding with a profile in the form of a letter S; having the outline of a reversed curve.

OHAG:  Occupational Health Assessment Guide (Health Canada).

OHS:  Occupational Health and Safety; sometimes Occupational Safety and Health.

Ohm’s Law: States that, in a given electrical circuit, the amount at current in amps is equal to the pressure in volts divided by the resistance in ohms. The formula is: I (Current) = V voltage or V = I x R R resistance or R = V/I.

Ohmmeter: In electrical contracting, a device to measure the resistance across a load. They are never used on a live circuit. Used to track down broken wires.

Oil: A liquid fossil fuel, is formed from layers of buried plants and animals that have been subjected to geologic heat and pressure over a long period of time. The energy that the plants and animals originally obtained from the sun is stored in the oil in the form of carbon. In addition to carbon, oil contains elements such as nitrogen, sulfur, mercury, lead, and arsenic. Oil is a nonrenewable resource because it cannot be replenished on a human time frame.

Oil Aerosol:  A suspension of fine solid or liquid particles in a gas.

Oil Bath Filter:  A labyrinth type filter having the active surfaces continuously splashed with oil. Most pollutants are absorbed by the oil which when circulated releases its pollutants, which sink by gravity to the bottom of the oil pan.

Oil-Canning: The term describing distortion of thin-gauge metal panels which are fastened in a manner restricting normal thermal movement.

Oil Free Compressor:  A positive displacement air compressor which has no oil injected into the compression chamber for lubrication, cooling or sealing

Oil Heating System: Refers to a central heating system that uses #2 fuel oil, kerosene, or residual oil as the primary fuel for heat generation.

Oil System:  Consists of a vessel which is a combination of oil sump and oil separator, an oil cooler and an oil filter.

Oil Trap:  A device to trap oil from leaving the compressor and entering the system.

Olefin: A class of unsaturated hydrocarbons having the general formula CnH2n.

OLF: (From “olfactory”) A perceived air quality term which attempts to quantify a given pollution load. One person creates 1 olf of bioeffluents. If there are 10 cubic meters of floor space per person, then people create 0.1 olf per m² (olf/m²). Other sources are compared and quantified by olfs. For example, if 40% of the people smoke, this adds 0.2 olf/m² to the load.

Olfactory Fatigue:  A condition in which a person’s nose, after exposure to certain odors, is no longer able to detect the odor.

Olfactory Nerve:  The nerve which senses and converts the Odor molecules to electrical signals for the brain to use.

Omnivore: Animal that obtains its nutrients from both plants and animals.

Onboard Diagnostics: Devices that are incorporated into the computer systems of new motor vehicles to monitor components and systems that affect emissions when malfunctioning. If a problem is detected, the OBD system illuminates a warning lamp on the vehicle instrument panel to alert the driver. This warning lamp typically contains the phrase Check Engine or Service Engine Soon. The system will also store important information about the detected malfunction so that a repair technician can accurately find and fix the problem.

Onboard Vapor Recovery: Devices placed on vehicles to capture gasoline vapor during refueling and then route the vapors to the engine when the vehicle is started so that they can be efficiently burned.

On Center (O.C.): A measurement term meaning a certain distance between like materials. Studs rafters, joists, and the like in a building placed at 16 inches O.C. will be laid out so that there is 16 inches from the center of one stud to the center of the next.

On-Line:  The condition when a computer or data center is operating and available to process information.

On Site:  Within the boundaries of the LLNL Livermore site or Site 300 properties.

Onsite Septic Disposal System (OSDS):  See disposal system.

Onychomycosis:  Invasive fungal infections of the nail.

Opacity: The amount of light obscured by particulate pollution in the air; clear window glass has zero opacity, a brick wall is 100 percent opaque. Opacity is an indicator of changes in performance of particulate control systems.

Open Area:  Pore area of a filter medium, often expressed as a percentage of the total area.

Open-Combustion Heater: A heating device that takes its combustion air from the surrounding room air.

Open-circuit:  See open-circuit SCBA.

Open-circuit Respirator:  See open-circuit SCBA.

Open-circuit SCBA:  A type of atmosphere-supplying respirator where the air is provided from a compressed breathing air source and the used (exhaled) air is expelled to the surrounding atmosphere; see closed-circuit SCBA.

Open Compressor:  A compressor where the motor is not sealed inside the compressor itself. 

Open-Face Filter:  A filter with no restrictions over the ends or faces of the unit, as opposed to the enclosed filter with reduced-size end connections.

Open Hole Inspection: When an engineer (or municipal inspector) inspects the open excavation and examines the earth to determine the type of foundation (caisson, footer, wall on ground, etc.) that should be installed in the hole.

Open Loop:  A system where water is pumped from a water well, pond, lake or other surface source for use in a heat pump.

Open-Loop Process:  Any process that does not fit the definition of “closed-loop process.”

Open-Loop Recycling:  A recycling system in which a product made from one type of material is recycled into a different type of product (e.g., used newspapers into toilet paper). The product receiving recycled material itself may or may not be recycled.

Open Mouth Technique: Effective method for inhaling medicine from a metered dose inhaler. See closed mouth technique.

Open Valley: Method of valley construction in which shingles on both sides of the valley are trimmed along a chalk line snapped on each side of the valley. Shingles do not extend across the valley. Valley flashing is exposed.

Open Weave: Fabrics are constructed such that, when viewing the fabric perpendicular to its surface, you can see through the holes formed by the interwoven fibers.

Operating Cost:  Cost of running your home comfort system, based on energy usage.

Operating Pressure:  The gauge pressure at which a pressure vessel is maintained in normal operation.

Operating Pressure Burst:  Above this pressure, the system may rupture or burst.

Operating Radius:  The Operating Radius of a vacuum cleaner takes into account the power cord and the hose length of the unit and calculates how far away from an electrical outlet the vacuum cleaner can be effectively used. This specification is useful to determine how often the user will have to find a new outlet during cleaning. Also referred to as “Operation Radius.”

Operative Temperature (to):  The uniform temperature of a radiantly black enclosure in which an occupant would exchange the same amount of heat by radiation plus convection as in the actual non-uniform environment. Operative temperature is numerically the average, weighted by respective heat transfer coefficients (hc and hr), of the air (ta) and mean radiant temperatures (tr).  to = (hcta + hrtr)/hc+hr)  At air speeds of 80 fpm (0.4 m/s) or less and tr less than 120 F,(50oC) operative temperature is approximately the simple average of the air and mean radiant temperatures and equal to the adjusted dry bulb temperature.

Ophiolite:  Any of a group of igneous and metamorphic rocks found within the continental crust, thought to be formed by the uplift of oceanic crust.

OPI:  Office of Primary Interest.

Opposed-Blade Damper: A type of damper where the blades rotate in the opposite direction.

O-Probe: A method used to test HEPA and ULPA filters for leaks utilizing either an aerosol photometer or discrete-particle counter. A sampling probe is moved in a series of parallel, slightly overlapping strokes across the test area at a distance of approximately 2.5cm (1 inch) from the filter face.

Optimum Operative Temperature:  Temperature that satisfies the greatest possible number of people at a given clothing and activity level.

Optimum Value Engineering (OVE):  Sometimes referred to as Advanced Framing. OVE Framing techniques use less lumber and therefore improve a structure’s level of insulation. Techniques include 24-inch on-center stud layout, single top plates, engineered header sizes, and special corner and wall configurations.

Organic: (1.) Any compound containing carbon. (2.) Substances derived from living organisms.

Organic Compounds:  Chemicals that contain carbon. Volatile organic compounds vaporize at room temperature and pressure. They are found in many indoor sources, including many common household products and building materials.

Organic Chemicals: Naturally occurring (animal or plant-produced or synthetic) substances containing mainly carbon, hydrogen, nitrogen, and oxygen.

Organic Dust Toxic Syndrome (ODTS):  Fever characterized by rapid onset after exposure to high organic dust levels. It is not well understood but thought to be too rapid to be an immune response.

Organic Farming:  Avoiding the use of synthetic chemicals as fertilizers, pesticides, and herbicides when farming.

Organic Felt: An asphalt roofing base material manufactured from cellulose fibers.

Organic Nitrogen:  All substances in which nitrogen is bonded to carbon.

Organic Peroxide: An organic compound that contains the bivalent -O-O- structure and which may be considered to be a structural derivative of hydrogen peroxide where one or both of the hydrogen atoms has been replaced by an organic radical.

Organic Phosphate:  Phosphate that is bound to plant or animal tissue.

O-Ring: Round rubber washer or gasket that is compressed to create a watertight seal, typically in a compression fitting.

Orientation: The azimuth of a particular surface or the major axis of a building. see Azimuth.
 
Oriented Strand Board (OSB, Chip Board, Wafer Board): A manufactured wood panel made out of 1”- 2” wood chips and glue. Often used as a substitute for plywood in the exterior wall and roof sheathing.

Orifice: A hole in a gas pipe or nozzle fitting where gas or fuel oil exits to be mixed with air before combustion occurs in the heating chamber

Orthopnea: Difficulty breathing related to body position, especially shortness of breath while lying on the back. This is often treated by propping the person’s head on two or more pillows while lying down.

Oscillating Fan:  A fan, usually portable, that moves back and forth as it operates, changing the direction of the air movement.

OS&H:  Occupational Safety and Health.

OSI (Ounces per square inch): A unit of pressure equal to one 1/16 PSI or 1.733 inches of water.

OSH:  Occupational Safety and Health.

OSHA:   Occupational Safety and Health Administration.

OSHA 300 Log: Used by employers to record all work-related injuries and illnesses.

Osmosis:  Diffusion of a liquid through a semi-permeable membrane from a dilute solution into a more concentrated solution, thus tending to equalize the concentration of each side of the membrane.

OTC:  OTC is a short-form for “over the counter,” and it is used to refer to drugs which can be bought without a prescription. Perhaps you keep children’s ibuprofen on hand for your child’s fever. You might also have a bottle of aspirin or Tylenol for headaches. Perhaps you have something for heartburn in your medicine cabinet. These products are OTC pharmaceuticals, which you can buy without prescription for your family’s use.

Other Triggers to Allergy:  In addition to these common allergy triggers there are other factors in the environment that can make life difficult for airborne allergy sufferers.

• Air pollution: High concentrations of nitrogen dioxide, sulphur dioxide and other chemicals that find their way into the atmosphere can irritate the nose and airways even in those who do not suffer from airborne allergy. One of the effects of the late phase allergic response is to make the nasal passages more sensitive to irritants – something called nasal hyper-responsiveness.
• Other irritants: Smoke (particularly tobacco), strong smells, perfumes, changes in temperature, or humidity can all provoke symptoms in people who have developed this extra sensitivity (nasal hyper-responsiveness).
• Diesel fumes: Importantly, there is another factor concerning irritants and pollution in the air. As well as provoking symptoms, by weakening the delicate nasal lining, irritants may increase susceptibility to allergy triggers. Research has shown that diesel particles in the air make people more sensitive to an allergy trigger.
• Air-conditioned atmospheres: In a person whose nasal lining has been made extra sensitive by repeated allergic attacks, the atmosphere in the work place can provoke symptoms of an airborne allergy even without allergy triggers in the air. Non-allergy, irritant triggers are often found in an air conditioned atmosphere. Chemicals, pollution sucked from outside, changes in air temperature, dust, low humidity and other factors in the ‘sick building syndrome’ can all provoke symptoms. Even good air conditioning, with efficient air filters, while it may reduce the level of pollen, will not eliminate all air pollution.

More research is needed to fully reveal the closest links between environmental pollution and allergic rhinitis.
Otitis Media:  Inflammation of the middle ear, or tympanum.

Otolaryngologist:  Pronunciation (ō′tō-lar′ing-gol′ŏ-jist).  A physician who specializes in otolaryngology

Otomycosis:  A superficial fungal infection of the outer ear canal.

Otoscope:  Pronunciation (ō′tō-skōp).  An instrument for examining the ear.
[oto- + G. skopeō, to view].

Outdoor Air:   Air taken from the external atmosphere and, therefore, not previously circulated through the system.

Outdoor Air Intake:  An opening in the building exterior that is a planned entry point for outdoor air.

Outdoor Air Supply: Air brought into a building from the outdoors (often through the ventilation system) that has not been previously circulated through the system. Also known as "Make-Up Air."

Outdoor Coil (also Condenser Coil):  In a heat pump, it takes in heat to warm your home. In an air conditioner, it dissipates heat from the refrigerant, changing the refrigerant from vapor to liquid to cool your home.

Outgas:  Emission of fumes into the air; these emissions are often caused by building materials that contain certain chemicals.

Outgassing:  The passive liberation of a gas from any material.

Outlet, Ceiling:  A round, square, rectangular, or linear air diffuser located in the ceiling, which provides a horizontal distribution pattern of primary and secondary air over the occupied zone and induces low velocity secondary air motion through the occupied zone.

Outlet Pressure:  Downstream pressure. Pressure exiting the outlet side of the filter.

Outlet, Slotted:  A long, narrow air distribution outlet, comprised of deflecting members, located in the ceiling sidewall, or sill, with an aspect ratio greater than 10, designed to distribute supply air in varying directions and planes, and arranged to promote mixing of primary air and secondary room air.

Outlet, Vaned:  A register or grille equipped with vertical and/or horizontal adjustable vanes.

Outlet Velocity:  The average velocity of air emerging from the outlet measured in the plane of the outlet.

Output:  The part of the circuit where the process signal is available.

Output Capacity: The conversion rate of useful heat that a heating unit produces after accounting for any waste caused by the conversion of energy into heat.

Outrigger: An extension of a rafter beyond the wall line. Usually a smaller member nailed to a larger rafter to form a cornice or roof overhang.

Outside Air: External air, atmosphere exterior to refrigerated or conditioned space, ambient (surrounding) air.

Outside Air Opening:  Any opening used as an entry for air from outdoors.

Overcast Sky: A sky in which there is no direct solar radiation. NOTE: The measured temperature data and solar radiation tables for overcast skies within this Handbook refer to days when the cloud cover was 8/8 during all the daylight hours. Night-time temperature data are related to the same 'overcast' days, i.e. night-time cloud cover was not taken into account.

Overhang: That part of the roof structure which extends horizontally beyond the vertical plane of the exterior walls of a building.

Overheating Protection:  See “Safety Shut-Off.”

Overhung Type Centrifugal Compressor:  A single inlet compressor with the impeller or impellers mounted on an extended shaft of the driver.

Overpressure Accumulation:  The permitted increase in pressure developed after the valve has opened. Usually expressed in percentage, i.e.; 3% accumulation (A.S.M.E. Code, Section I). Flows through safety/relief valves are officially determined at these overpressure conditions.

Overshoot:  The growth beyond an area’s carrying capacity, which leads to a “crash.”

Oversized Evaporator:  An evaporator with a greater capacity than the nominal capacity of the system. 

Oxidant: A collective term for some of the primary constituents of photochemical smog.

Oxidation:   (1) A substance containing oxygen that reacts chemically to produce a new substance. (2) A reaction in which oxygen combines with another substance.

Oxidizer: A substance, other than a blasting agent or explosive, that initiates or promotes
combustion in other materials, thereby causing fire either of itself or through the release of oxygen or other gases.

Oxidizing Agent:  Any substance, such as oxygen (O 2) or chlorine (Cl 2), that will readily add (take on) electrons. The opposite is a reducing agent.

Oxygen: A colorless, odorless gas

Oxygen, Compressed: A form of prescribed oxygen that is stored in a tank in gas form. A flow meter and a regulator are attached to the tank to adjust the oxygen flow. The compressed oxygen system is generally prescribed when oxygen is not needed all the time, such as only when walking or performing physical activity.

Oxygen Concentrator: An electric oxygen delivery system about the size of a large suitcase. The concentrator extracts some of the air from the room and separates the oxygen from other gases in the air. Oxygen is then delivered to you through a nasal cannula. An oxygen concentrator may be recommended if you need oxygen all the time or while sleeping.

Oxygen, Liquid: At very cold temperatures, oxygen changes from a gas to a liquid. When liquid oxygen is warmed, it becomes a gas so that it can be delivered to you. A liquid oxygen system includes a large stationary unit that stays in the home. It also includes a small, portable canister (weighing from 5 to 13 pounds) that can be filled from the stationary unit for trips outside the home.

Oxygenate: An organic molecule that contains oxygen. Oxygenates are typically ethers and alcohols.

Oxygen Depletion Sensor: A safety device on a heating unit that shuts off the fuel supply to the combustion chamber when oxygen is depleted.

Oxygen Deficiency:  A condition based on an oxygen concentration or partial pressure below which a person may adversely affected; each authority having jurisdiction may establish an alternative definition; see hypoxia; refer to CSA Z94.4 for the definition.

Oxygen Deficient Atmosphere:  An atmosphere with an oxygen content below 19.5% by volume; or an atmosphere with an oxygen content below a given percentage by volume as defined by the authority having jurisdiction.

Oxygen-Enriched Atmosphere:  An atmosphere containing more than 23.5 percent oxygen by volume.

Oxygen-generating:  A type of closed-circuit SCBA, which combines the moisture and carbon dioxide from the user’s exhaled breath with a solid oxygen-generating chemical to produce air that is stored in a reservoir and supplied to the user upon inhalation.

Oxygen Re-breathing:  A type of closed-circuit SCBA, which adsorbs carbon dioxide and adds pure gaseous oxygen from a cylinder to replace consumed oxygen.

Ozone: A gas that is a variety of oxygen. The oxygen gas found in the air consists of two oxygen atoms stuck together; this is molecular oxygen. Ozone consists of three oxygen atoms stuck together (O3) into an ozone molecule. Ozone occurs in nature; it produces the sharp smell you notice near a lightning strike. High concentrations of ozone gas are found in a layer of the atmosphere — the stratosphere — high above the Earth. Stratospheric ozone shields the Earth against harmful rays from the sun, particularly ultraviolet B. Smog's main component is ozone; this ground-level ozone is a product of reactions among chemicals produced by burning coal, gasoline and other fuels, and chemicals found in products including solvents, paints, hairsprays, etc.

Ozonation:  The application of ozone to water or air-space for disinfection or for taste and odor control.

Ozone Action Day: A day on which the ozone levels are predicted to reach unhealthy levels.  (Also called Clean Air Action Days.)

Ozone Depletion: The reduction in the stratospheric ozone layer. Stratospheric ozone shields the Earth from ultraviolet radiation. The breakdown of certain chlorine and / or bromine-containing compounds that catalytically destroy ozone molecules in the stratosphere can cause a reduction in the ozone layer.

Ozone-Forming Potential: (See Reactivity.)

Ozone Generator:  A product designed to emit large amounts of ozone. Sometimes sold as “air purifiers.” Some studies indicate that these products can exceed health standards. Are considered by the EPA to be generally ineffective in controlling indoor air pollution.

Ozone Hole: Thin place in the ozone layer located in the stratosphere high above the Earth. Stratospheric ozone thinning has been linked to destruction of stratospheric ozone by CFCs and related chemicals. The 1990 Clean Air Act has provisions to reduce and eliminate ozone destroying chemicals' production and use. Ozone holes have been found above Antarctica and above Canada and northern parts of the United States, as well as above northern Europe.

Ozone Layer: A layer of ozone in the lower portion of the stratosphere – 12 to 15 miles above the Earth’s surface – which helps to filter out harmful ultraviolet rays from the sun. It may be contrasted with the ozone component of photochemical smog near the Earth’s surface which is harmful.