Glossary of HVAC and Environmental Control Terms


General Terms (Used on this website)

This page highlights HVAC definitions for many of the terms found on our website.

What it is: A device used to regulate the temperature, humidity, filtration, and/or pressurization in a given space.

Why it matters: Air Innovations creates Environmental Control Units (ECU) that solve problems in customers’ unique or demanding environments.

What it is: These systems utilize an air-cooled condenser, the device used to remove the heat generated in the vapor compression cycle.

Why it matters: Most HVAC systems use air to cool systems. These systems are used when no source of water is available for condensing and are optimal for portable applications. We also offer water-cooled or chilled-water environmental control units.

What it is: The removal of airborne contaminants from the air.

Why it matters: Air Innovations products use a variety of techniques to purify the air. We use HEPA or ULPA filtration (based on the application) and activated carbon to eliminate foreign particles and gases from the air. Products such as Isolation Air (for quarantine and hospital contamination control) and Cleanroom Systems use these techniques.

In some environments, such as bedrooms of asthmatics, our products use filtration along with introducing pre-filtered outside air to both remove particles from the air, but also to dilute the presence of volatile organic compounds (VOCs) (see the HepAir X100 air cleaner).

What it is: An abbreviation for Cubic Feet per Minute.

Why it matters: This measurement lets you know how much airflow you’ll get from an ECU or other HVAC equipment. It helps you understand whether the ECU/HVAC system has enough capacity to cool the space you are trying to cool.

What it is: These devices utilize chilled water (typically 42-45 °F or 5-7 °C) instead of direct-expansion refrigerant to cool the designated space. These are different from water-cooled environmental control systems, since they require only the chilled-water and a fan to control the temperature in a space. However, these systems require a year-round source of chilled water, supplied by the facility where they are installed.

Why it matters: Laboratories with significant heat output and other similar environments that require a year-round supply of chilled water can use a chilled-water ECU to cool the designated space.

What it is: A device used to turn a chemical from its gaseous form into its liquid form. A condensing unit is part of all HVAC systems. The condenser transfers the heat extracted via the evaporator to someplace outside the system (via water or air). In other words, in the process of cooling, heat is generated and needs to be moved somewhere else – the condenser does this. Examples of condensers are the air conditioning unit many people have outside their homes or the outside portion of a window air-conditioning unit.

Why it matters: This is a basic principle of most air conditioning. Most equipment Air Innovations builds is self-contained with a condenser as part of the package. Remote air-cooled condensers are available depending on the application.

What it is: The temperature at which the water vapor in the air condenses into water. [More technically, it is the temperature at which the water vapor in the air condenses at the same rate at which it evaporates at constant barometric pressure].

Why it matters: Cooling air below the dew point is how you dehumidify the air. Dew point control is critical in some applications such as tablet coating for pharmaceuticals, desiccant drying in cleanroom control for aerospace applications, and many others. Air Innovations designs systems controlling dew point/relative humidity, filtration, and other environmental control factors.

What it is: An environmental control unit (ECU) that uses a cycle of refrigerant vapor expansion and compression to cool a space. DX systems cool the air in a space by flowing supply air over the evaporator portion of the system.

Why it matters: Air Innovations uses this method in its packaged/integrated and split systems. This is a basic principle of most air conditioning.

What it is: A device used to turn a chemical from its liquid form into its gaseous form. An evaporator is part of an HVAC system. The evaporator absorbs heat from the area to be cooled to the liquid inside the HVAC system. An example is the indoor portion of a window air-conditioning unit.

Why it matters: This is a basic principle of most air conditioning.

What it is: A freestanding ECU is not contained within another piece of equipment. These may be installed in one place or mobile.

Why it matters: Many applications, such as semiconductor clean rooms, floral display cases, and mobile quarantine units require environmental control in a specific room or area. Air Innovations has standard freestanding ECU products in some common categories (floral cooling displays) and designs custom product freestanding ECUs for clean room HVAC and many other applications. See also Integrated ECU.

What it is: The resolved upon strategy to overcome a problem in heating, ventilation, and air conditioning.

Why it matters: This is what Air Innovations does best – come up with solutions to challenges in HVAC!

What it is: The resolved upon strategy to overcome a problem in heating, ventilation, air conditioning, or refrigeration.

Why it matters: Some of our users refer to this instead of HVAC, since it’s more inclusive. We work in this sphere as well.

What it is: This is a system designed by Air Innovations that becomes part of another company’s products.

Why it matters: Some equipment requires special temperature, humidity, pressure, or filtration internally to operate properly. Air Innovations has a long history of designing environmental control sub-systems with critical applications from medical equipment to oil & gas slurry processing. See also Freestanding ECU.

What it is: Psychrometry is the field of engineering concerned with the determination of physical and thermodynamic properties of gas-vapor mixtures. A psychrometric facility is a space that allows for the study of these properties.

Why it matters: The presence of our on-site psychrometric facility allows us to test products under a variety of conditions, simulating most conditions under which our products will actually operate. For example, the room can achieve temperatures between 0°F and 120°F (-17°C and 48°C) at ±2.5% RH and can test products at 115V to 277V (1 phase) or 208V to 460V (3 phase).

What it is: A measure of the amount of water vapor in the air relative to the maximum amount of moisture the air could hold.

Why it matters: Too much or too little humidity can cause equipment to malfunction or goods, like wine, to degrade faster than they should. Air Innovations can design humidity control into its systems. The company also has standard products with integrated humidity monitors and control. We also provide stand-alone wine cellar humidifiers.

What it is: Any air conditioning that has unique requirements. Typically we refer to specialty air conditioning when additional factors (such as pressure, relative humidity, or filtration) are important in the process OR when precise tolerances are required in an application.

Why it matters: Our focus in on innovative thinking for unique circumstances. Challenge us with your specialty air conditioning requirements today!

What it is: An environmental control solution in which the evaporating unit and condensing unit are not part of the same physical unit. The system achieves the same results as a wholly integrated system, but allows for greater versatility during installation.

Why it matters: Users with constrained spaces they are cooling or those looking for a quieter system in the cooled space should consider using a split system. Air Innovations can provide air-cooled split systems.

What it is: Like it sounds, these systems use water cooled condensers. These are different from chilled-water environmental control systems in that they can use a much warmer water temperature to reject the heat from the system via the condenser.

Why it matters: People with limited space for ductwork or who are sensitive to noise in the area that needs temperature control, but who have access to a water source for cooling (reservoir, geothermal, etc.) can opt for this type of solution. Water-cooled environmental control units are seen as being more environmentally conscious. Air Innovations is the only major provider of water-cooled systems for wine cellars, etc. Tell us about your project today.

Application Specific Terms

What it is: A device that creates a cavity/pocket which holds food or pharmaceuticals; the cavity/pocket is generally comprised of thermoformed plastic backed with a seal (often aluminum foil or plastic), but can also be made with a cold-forming process. Blister packs are often used to offer protection against contamination or tampering and to control dosages of pharmaceutical tablets.

Why it matters: Air Innovations works with customers in blister-packaging applications (and other pharmacological applications) to ensure precision process control for pharmaceuticals.

What it is: This site uses this term to refer to environmental control within a space that requires a low level of environmental pollutants (vapors, dust, powders, microbes, aerosols, etc.).

Why it matters: Air Innovations works with all Clean Room classifications (ISO 1 to ISO 9). Air Innovations has an entire brand dedicated to Clean Room Environmental Control and air conditioning.

What it is: Environmental-control equipment designed and tested to ensure it does not initiate an explosion. This is often referred to as “severe duty” equipment. This should not to be confused with “blast proof” which implies a design that can withstand certain levels of explosions.

Why it matters: Explosions can be caused by a variety of sources (arcing, heat generation, etc.). Equipment that generates significant amounts of heat requires a heat-exhaust method, while equipment subject to an environment with ignitable vapors, gases, dust, or other material requires absolute separation of sparking devices and volatile gases to prevent explosions. Air Innovations works within a wide range of environments to create an explosion-proof design for any customer working in similar environments.

What it is: On this website, we consider harsh environments those in which typical equipment would fail unusually quickly (or immediately).

Why it matters: Air Innovations makes environmental control equipment that can operate from -40°C to +54°C (-40°F to +130° F) and in environments with high salt or high dust content. Learn more in this sample project that existed in a harsh environment: Portable Air-Cooled ECU for an aerospace application.

Broadly speaking, this refers to any mechanism that can detect and destroy a missile before the missile inflicts damage. Most often, Air Innovations uses the term as applied to tactical ballistic missile defense systems.

Why it matters: Missile defense systems typically use lasers to track targets. These lasers must remain precisely calibrated to ensure accuracy and their calibration must be performed under highly controlled conditions. Air Innovations created a portable, self-contained HVAC system that provides cleanroom-level conditions for recalibration of the lasers. You don’t want your targeting lasers to fail when you’re shooting down incoming missiles!

What it is: A device used to repair, fix or counteract the effects of photomask defects using nanomachining (features or structures substantially smaller than a micron) techniques.

Why it matters: One of the biggest challenges in using lithography in high-volume semiconductor fabrication is photomask defectivity (see this SPIE article). Air Innovations has created an environmental control unit (ECU) for a nanomachining mask repair tool system.

What it is: “Non-condensing” means a vapor is not changing to a liquid. This condition exists when the temperature to which the gas is exposed is above the dew point (the temperature at which the water vapor in the air will begin to condense into water).

Why it matters: When designing niche environmental control units, it’s important to know the typical and extreme conditions the system will be operating in. Water forming inside a system can obviously cause a lot of problems – we work to prevent those problems from happening in your system.

What it is: In some industrial systems, substances with given structure or properties (chemicals) are used to create a specific environment or set of actions that lead to some desired result. For example, a company may use a chemical to improve product quality or increase the speed of a particular process.

Why it matters: Since a chemical’s properties can change with fluctuations in temperature, humidity, or other environmental factors, we generally discuss the environmental control of process chemicals on this website. Our customers are typically trying to maintain a specific environment for the chemical itself so they get the same results in their process each time, even in demanding situations. Check out how we helped one customer whose equipment operated 24/7 in a medical application that required strict humidity and temperature control in a small space with no defrost interruptions.

What it is: Designed to be shock resistant.

Why it matters: Some equipment – especially in mobile and military HVAC applications – are subject to unstable environments. At Air Innovations, we can design specialty HVAC systems that survive in harsh and rugged environments. When customers require this, we perform drop tests to ensure the ECU keeps working even after a drop occurs!


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