A tapered element oscillating microbalance (TEOM) is an instrument used for real-time detection of aerosol particles by measuring their mass concentration. It makes use of a small vibrating glass tube whose oscillation frequency changes when aerosol particles are deposited on it increasing its

inertia Inertia is the idea that an object will continue its current motion until some force causes its speed or direction to change. The term is properly understood as shorthand for "the principle of inertia" as described by Newton in his first law o ...

. TEOM-based devices have been approved by the

U.S. Environmental Protection Agency The Environmental Protection Agency (EPA) is an independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it be ...

for environmental air quality monitoring, and by the U.S.

Mine Safety and Health Administration The Mine Safety and Health Administration (MSHA) () is a large agency of the United States Department of Labor which administers the provisions of the Federal Mine Safety and Health Act of 1977 (Mine Act) to enforce compliance with mandatory safe ...

for monitoring

coal dust Coal dust is a fine powdered form of which is created by the crushing, grinding, or pulverizing of coal. Because of the brittle nature of coal, coal dust can be created during mining, transportation, or by mechanically handling coal. It is a form ...

exposure for miners to prevent several respiratory diseases.

Operation

Tapered element oscillating microbalance diagram static

The TEOM uses a hollow glass tube as a

microbalance A microbalance is an instrument capable of making precise measurements of weight of objects of relatively small mass: of the order of a million parts of a gram. In comparison, a standard analytical balance is 100 times less sensitive; i.e. it ...

. Incoming particles are deposited on a filter at the tip of the tube, and the added mass causes a change in its oscillation frequency which is detected electronically. The element is periodically cycled to return it to its natural frequency. The inlet to the device only allows particles of the desired size range to enter. TEOM devices operate continuously and do not need filter changes as frequently as high-volume air samplers. Mechanical noise and dramatic temperature fluctuations can interfere with the operation of a TEOM device. In addition, water droplets cannot be distinguished from particle mass, so the device must adjust the incoming air temperature to cause water droplets to evaporate, or contain a dryer or humidity sensor to adjust the readings. Under ideal conditions, TEOM is just as accurate as the standard reference method, but its sensitivity presents complications for use for environmental monitoring in urban areas. A filter dynamic measurement system (FDMS) can be used to adjust for the volatile component of the mass. TEOM has poor sensitivity to semi-volatile particles due to the temperature and humidity conditions used. TEOM instruments with FDMS alternate between a base cycle and a reference cycle, the latter of which measures the mass loss of the filter when clean air is passed through it, allowing the mass loss during the base cycle to be estimated. It is important that the air conditioning system not cycle over the same period as the TEOM instrument, because this can cause

aliasing In signal processing and related disciplines, aliasing is an effect that causes different signals to become indistinguishable (or ''aliases'' of one another) when sampled. It also often refers to the distortion or artifact that results when ...

Applications

Instruments using TEOM have been designated as

Federal Equivalent Method The U.S. National Ambient Air Quality Standards (NAAQS, pronounced ) are limits on atmospheric concentration of six pollutants that cause smog, acid rain, and other health hazards. Established by the United States Environmental Protection Agency ...

s by the

for environmental air quality monitoring of both coarse and fine

particulate matter Particulates – also known as atmospheric aerosol particles, atmospheric particulate matter, particulate matter (PM) or suspended particulate matter (SPM) – are microscopic particles of solid or liquid matter suspended in the air. The t ...

(PM₁₀, PM_2.5, and PMc). TEOM instruments are faster than and avoid difficulties with beta attenuation and

quartz crystal microbalance A quartz crystal microbalance (QCM) (also known as ''quartz microbalance'' (QMB), sometimes also as ''quartz crystal nanobalance'' (QCN)) measures a mass variation per unit area by measuring the change in frequency of a quartz crystal resonator. Th ...

(QCM) methods. TEOM is the basis for a continuous personal dust monitor (CPDM) for

in mines, to protect workers from exposure to coal mine dust which leads to

black lung disease Coal workers' pneumoconiosis (CWP), also known as black lung disease or black lung, is an occupational type of pneumoconiosis caused by long-term exposure to coal dust. It is common in coal miners and others who work with coal. It is similar to bo ...

and progressive massive fibrosis. Prior to the introduction of CPDMs, dust particles collected on a filter needed to be analyzed in a laboratory, leading to a delay of weeks in obtaining results. Continuous monitoring allows miners to take corrective action such as moving to another area or changing their activities if dust levels exceed exposure limits. In one study this led to a 90% reduction in samples exceeding the dust exposure limit. In February 2016, the U.S.

(MSHA) mandated the use of CPDMs on working sections of underground coal mines, and for workers who have evidence of the development of

pneumoconiosis Pneumoconiosis is the general term for a class of interstitial lung disease where inhalation of dust ( for example, ash dust, lead particles, pollen grains etc) has caused interstitial fibrosis. The three most common types are asbestosis, sili ...

. As of 2017, the only CPDM instrument approved by MSHA uses a TEOM. As of 2013, TEOM was not considered suitable for workplace monitoring of

nanomaterials * Nanomaterials describe, in principle, materials of which a single unit is sized (in at least one dimension) between 1 and 100 nm (the usual definition of nanoscale). Nanomaterials research takes a materials science-based approach to n ...

due to its cut-off particle sizes of 10, 2.5, or 1 μm, and the physical size of the instrument.

History

TEOM is a proprietary technology developed by Rupprecht and Patashnick Co., Inc. of

Albany, New York Albany ( ) is the capital of the U.S. state of New York, also the seat and largest city of Albany County. Albany is on the west bank of the Hudson River, about south of its confluence with the Mohawk River, and about north of New York Ci ...

, whose successor company (as of 2005) is

Thermo Fisher Scientific Thermo Fisher Scientific Inc. is an American supplier of scientific instrumentation, reagents and consumables, and software services. Based in Waltham, Massachusetts, Thermo Fisher was formed through the Mergers and acquisitions, merger of Ther ...

. "TEOM" is a registered trademark. It was originally developed as a fixed-site environmental particulate mass monitor, and TEOM aerosol detectors were available in 1981. Development of the continuous personal dust monitor was originally performed by Rupprecht and Patashnick Co., Inc. and continued by Thermo Fisher under contract from the U.S.

National Institute for Occupational Safety and Health The National Institute for Occupational Safety and Health (NIOSH, ) is the United States federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. NIOSH is part of the ...

with input from other government, labor, and industry organizations. Machine-mounted continuous dust monitors have been available since 1997.

Operation

Applications

History

References

Further reading