As an American manufacturer of vacuum chambers and their associated systems, Terra Universal offers an array of vacuum chamber designs for material testing, thermal testing, stress testing, degassing, atmospheric simulation, and more. In this series, we'll discuss smaller benchtop vacuum chambers for small parts, as well as large high-capacity vacuum chamber models for extra large assemblies or components. Additionally, we'll discuss configurable add-ons such as vacuum pumps, vacuum control modules, vacuum gloveboxes, and vacuum chamber material selection criteria. Whether it's a lab, cleanroom, or unspecified research environment, Terra offers thousands of ready-to-ship products, as well as custom-fabricated solutions for unique applications.
- Vacuum Chamber Pressure Measurement and Operation (You are Here)
- Vacuum Chambers for Stress and Pressure Testing
- Vacuum Chambers for Atmospheric Simulation and Testing
- Vacuum Chambers for Leak Testing, Vacuum Drying, Degassing
What Is a Vacuum Chamber?
A vacuum chamber is a rigid enclosure that maintains an extremely low-pressure environment and a near-perfect vacuum. Vacuum chambers require a vacuum pump to remove air and other gases from the chamber, creating a low-pressure environment inside. This environment is essential for various scientific research, industrial processes, and testing applications. The level of vacuum achieved can vary widely, depending on the specific requirements of the application, ranging from full vacuum to low vacuum
How Does a Vacuum Chamber Work and Operate?
All of Terra’s vacuum chambers include two metering valves: one for applying a vacuum from a pump and the other for backfilling the chamber with nitrogen or other process gases. A vacuum gauge reads the pressure levels inside the chamber within a range of 0 – 30” Hg. Terra's vacuum chambers can be customized to include precision needle valves for exact application, monitoring, backfill, and bleeding of vacuum pressure in increments of ~1" Hg (~3% vacuum). The hardware is mounted over an extra layer of acrylic to prevent damage to the lid while the chamber is under maximum vacuum.
Understanding Vacuum Pressure
Understanding vacuum pressure and its measurement is crucial for selecting and utilizing vacuum chambers effectively. By using the appropriate units and recognizing the pressure levels required for specific applications, researchers and engineers can ensure optimal performance and reliability of their vacuum systems.
In the context of measuring vacuum conditions for vacuum chamber applications, a 'near perfect vacuum' refers to extremely low pressures down to 10^-9 torr or even lower, depending on the precision and capabilities of the vacuum system. To put this in perspective, atmospheric pressure at sea level is about 760 torr. Thus, 10^-9 torr reflects remarkably low-pressure conditions, approximately 1 billionth of Torr, which renders an atmosphere that is almost entirely void of air and gas molecules.
The near absence of matter and consequently air molecules drastically reduces particle collisions and gaseous interference, which is essential in fields like material science, aerospace engineering, biotechnology research, and fields requiring precision measurements with high repeatability. This controlled setting enables precise experimentation and analysis by minimizing external variables such as air resistance or contaminants. For deep space exploration, vacuum chambers are crucial for testing the behavior of materials or devices in conditions that are akin to outer space or at the atomic scale where standard atmospheric conditions do not apply.
How Is Vacuum Pressure Measured? Scientific Units and Conversions

The measurement of vacuum pressure requires determining how much lower the pressure inside a space or chamber is compared to a known reference. Vacuum pressure applications are typically measured in torrs or millibars, with the measurement often expressed in millimeters of mercury (mmHg). When comparing vacuum chambers or other vacuum systems online, you may encounter several measurements listed, such as Torr (mmHg) or inches of mercury (inHg).
Worldwide, the International System of Units (SI) recognizes Pascal (Pa) as the standard measurement for pressure. Torr, mmHg, and inHg are no longer officially prescribed by the International System of Units (SI), yet remain popular for referencing pressure measurements.
- Inches of Mercury (inHg): One standard atmosphere is approximately equivalent to 29.92 inches of mercury.
- Torr and millimeters of mercury (mmHg): These units are common in low to medium vacuum measurements. One torr is equivalent to the pressure exerted by a 1 mm column of mercury.
- Pascals (Pa): In scientific contexts, especially where higher precision is needed, the SI unit pascal is used.
- Bars or millibars: Sometimes used for their proximity to atmospheric pressure units, especially in meteorology.
- Atmosphere (atm): The standard atmospheric pressure at sea level.
Vacuum Chamber Pressure Unit Equivalents (Table)
The table below lists vacuum levels and their corresponding measurements in different units such as Torr, millimeters of mercury (mmHg), and inches of mercury (inHg).
Vacuum Level | Torr | Millimeters of Mercury (mmHg) | Inches of Mercury (inHg) |
Low (Rough | 760 to 1 | 760 to 1 | 29.9213 to 0.0394 |
Medium | 1 to 10-3 | 1 to 0.001 | 3.9370 x 10⁻² to 3.9370 x 10⁻⁵ |
High | 10-3 to 10-7 | 0.001 to 1.0 x 10⁻⁷ | 3.9370 x 10⁻⁵ to 3.9370 x 10⁻⁹ |
Ultra High | 10-7 and below | 1.0 x 10⁻⁷ and below | 3.9370 x 10⁻⁹ and below |
Vacuum Pressure FAQ
Question: What is a Torr Unit of Pressure? (mmHg)
Answer: A "torr" is a unit of pressure used to measure atmospheric pressure. 1 torr is defined as exactly 1 mmHg, and therefore 1/760 of standard atmospheric pressure, and is equivalent to the pressure exerted by a 1 mm column of mercury. The mmHg unit of measurement is closely related to the concept of torr. The bar unit is commonly subdivided into millibars (mb), where 1000 mb equals 1 bar. In a barometric context, the standard atmospheric pressure at sea level is also defined as 1 atmosphere (atm).
Question: Why Are Terra's Vacuum Chambers Measured in Inches of Mercury (inHg)
Terra's vacuum chambers are measured in standard units with inches of mercury (inHg). A standard atmosphere is equivalent to approximately 29.92 inches of mercury. This unit has historical roots dating back to the invention of the mercury barometer, which was commonly used to measure atmospheric pressure. Therefore, vacuum pressure is commonly measured in inches of mercury (inHg) when using a mercury barometer or vacuum gauge, especially in the United States. Vacuum chamber manufacturers commonly use inches of mercury (inHg) as a unit of measurement because it provides a precise and easily interpretable way to quantify the level of vacuum, expressed as the height of a mercury column. A higher vacuum level corresponds to a greater height of mercury in the column.
Question: What is the Equivalent to Torr Units in Bar Units?
A bar is a unit of pressure in the metric system. 1 bar unit equates to exactly 100,000 pascals, and approximately 750.06 torr (mmHg). The use of inches of mercury (inHg) as a unit of atmospheric pressure has historical roots dating back to the invention of the mercury barometer and its adoption as a standard measurement device. Therefore, vacuum pressure is commonly measured in inches of mercury (inHg) when using a mercury barometer or vacuum gauge.
Need Help Configuring a Vacuum Chamber System?
As a manufacturer of vacuum chamber systems, Terra Universal offers a deep pool of factory expertise and end to end solutions with globally honored pricing and worldwide delivery.
Shop Terra Universal Online to browse a wide selection of vacuum chamber systems, accessories, and add-ons including chambers, vacuum pumps, vacuum feedthroughs, humidity control solutions, and nitrogen purge systems.
Contact us or request a quote for custom orders including atypical chamber sizes, gas purge solutions, vacuum pumps, feedthroughs, custom gauges, and other accessories.