 | This article has multiple issues. Please help improve it or discuss these issues on the talk page . (Learn how and when to remove these messages)
|
A particulate matter sampler is an instrument for measuring the properties (such as mass concentration or chemical composition) of particulates in the ambient air.
Two different types of particulate matter samplers exist that measure particulate mass concentration: manual samplers and automated samplers.
Manual samplers draw a known volume of air through a filter. The filter is weighed on an analytical balance before and after sampling, and the difference in weight divided by the volume of air pulled through the filter gives the mass concentration of the particulate. [1]
Automated samplers do the weighing in the field. There are two types of automated samplers in common usage: samplers that use a beta gauge for mass measurement and samplers that use a tapered element oscillating microbalance (TEOM) for mass measurement.
Beta gauge particulate samplers have an appearance that is similar to a reel to reel tape recorder. Air is pulled through a filter tape to accumulate a sample, the mass of the tape before and after sampling is determined by advancing the tape spot into the beta attenuation cell.
The tapered element oscillating microbalance (TEOM) particulate sampler operates by drawing air through a filter attached at the tip of a glass tube. An electrical circuit places the tube into oscillation, and the resonant frequency of the tube is proportional to the square root of the mass on the filter.
Recently, microphone based instruments have been devised that monitor noise levels in specific frequency bands to predict local PNC levels. Prototypes of such instruments have been tested in Europe and in Bangalore. [2]
Particles of different sizes have different health effects. Inertial separators are used to eliminate particles outside of the desired size range. If a gas stream containing particles of different sizes is forced to turn a sharp corner, the inertia of the large particles causes them to separate from the gas stream lines. The larger particles can be collected and removed from the gas stream after collisions with the walls of the vessel.
The two common types of inertial separators are cyclones, which spin the gas stream, causing collisions of the heavier particles with the outside of the cyclone wall, and impactors, where the gas particle stream is directed at a greased metal plate and turned at the last moment, causing the larger particles to stick to the greased plate.
Modern particulate samplers use a volumetric flow control system that pulls air through the particle separator at the velocity required to achieve the desired cutpoint.
For air pollution applications, the definition of "particulate" does not include uncombined water, and water from a particulate sample must be removed before it is weighed. This can be done either by heating the sample to evaporate the water or by placing the sample in a low humidity environment before weighing.
 | This section needs expansion. You can help by adding to it. (October 2024) |
An aerosol is a suspension of fine solid particles or liquid droplets in air or another gas. Aerosols can be generated from natural or human causes. The term aerosol commonly refers to the mixture of particulates in air, and not to the particulate matter alone. Examples of natural aerosols are fog, mist or dust. Examples of human caused aerosols include particulate air pollutants, mist from the discharge at hydroelectric dams, irrigation mist, perfume from atomizers, smoke, dust, sprayed pesticides, and medical treatments for respiratory illnesses.
A nephelometer or aerosol photometer is an instrument for measuring the concentration of suspended particulates in a liquid or gas colloid. A nephelometer measures suspended particulates by employing a light beam and a light detector set to one side of the source beam. Particle density is then a function of the light reflected into the detector from the particles. To some extent, how much light reflects for a given density of particles is dependent upon properties of the particles such as their shape, color, and reflectivity. Nephelometers are calibrated to a known particulate, then use environmental factors (k-factors) to compensate lighter or darker colored dusts accordingly. K-factor is determined by the user by running the nephelometer next to an air sampling pump and comparing results. There are a wide variety of research-grade nephelometers on the market as well as open source varieties.
Cyclonic separation is a method of removing particulates from an air, gas or liquid stream, without the use of filters, through vortex separation. When removing particulate matter from liquid, a hydrocyclone is used; while from gas, a gas cyclone is used. Rotational effects and gravity are used to separate mixtures of solids and fluids. The method can also be used to separate fine droplets of liquid from a gaseous stream.
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 is limited in precision to 0.1 milligrams. Microbalances are generally used in a laboratory as standalone instruments but are also incorporated into other instruments, such as thermogravimetry, sorption/desorption systems, and surface property instruments. It is the precision of the microbalance that distinguishes it from other weighing devices.
A dust collector is a system used to enhance the quality of air released from industrial and commercial processes by collecting dust and other impurities from air or gas. Designed to handle high-volume dust loads, a dust collector system consists of a blower, dust filter, a filter-cleaning system, and a dust receptacle or dust removal system. It is distinguished from air purifiers, which use disposable filters to remove dust.
A particle counter is used for monitoring and diagnosing particle contamination within specific clean media, including air, water and chemicals. Particle counters are used in a variety of applications in support of clean manufacturing practices, industries include: electronic components and assemblies, pharmaceutical drug products and medical devices, and industrial technologies such as oil and gas.
The term wet scrubber describes a variety of devices that remove pollutants from a furnace flue gas or from other gas streams. In a wet scrubber, the polluted gas stream is brought into contact with the scrubbing liquid, by spraying it with the liquid, by forcing it through a pool of liquid, or by some other contact method, so as to remove the pollutants.
Bioaerosols are a subcategory of particles released from terrestrial and marine ecosystems into the atmosphere. They consist of both living and non-living components, such as fungi, pollen, bacteria and viruses. Common sources of bioaerosols include soil, water, and sewage.
In granulometry, the particle-size distribution (PSD) of a powder, or granular material, or particles dispersed in fluid, is a list of values or a mathematical function that defines the relative amount, typically by mass, of particles present according to size. Significant energy is usually required to disintegrate soil, etc. particles into the PSD that is then called a grain size distribution.
Compressed air filters, often referred to as line filters, are used to remove contaminants from compressed air after compression has taken place.
In the physics of aerosols, aerosol impaction is the process in which particles are removed from an air stream by forcing the gases to make a sharp bend. Particles above a certain size possess so much momentum that they can not follow the air stream and strike a collection surface, which is available for later analysis of mass and composition. Removal of particles from an air-stream by impaction followed by mass and composition analysis has always been a different approach as to filter sampling, yet has been little utilized for routine analysis because of lack of suitable analytical methods.
Indoor bioaerosol is bioaerosol in an indoor environment. Bioaerosols are natural or artificial particles of biological origin suspended in the air. These particles are also referred to as organic dust. Bioaerosols may consist of bacteria, fungi, viruses, microbial toxins, pollen, plant fibers, etc. Size of bioaerosol particles varies from below 1 μm to 100 μm in aerodynamic diameter; viable bioaerosol particles can be suspended in air as single cells or aggregates of microorganism as small as 1–10 μm in size. Since bioaerosols are potentially related to various human health effects and the indoor environment provides a unique exposure situation, concerns about indoor bioaerosols have increased over the last decade.
An aethalometer is an instrument for measuring the concentration of optically absorbing (‘black’) suspended particulates in a gas colloid stream; commonly visualized as smoke or haze, often seen in ambient air under polluted conditions. The word aethalometer is derived from the Classical Greek verb aethaloun, meaning "to blacken with soot". The aethalometer, a device used for measuring black carbon in atmospheric aerosols, was initially deployed in 1980 and was first commercialized by Magee Scientific.
Aerosol mass spectrometry is the application of mass spectrometry to the analysis of the composition of aerosol particles. Aerosol particles are defined as solid and liquid particles suspended in a gas (air), with size range of 3 nm to 100 μm in diameter and are produced from natural and anthropogenic sources, through a variety of different processes that include wind-blown suspension and combustion of fossil fuels and biomass. Analysis of these particles is important owing to their major impacts on global climate change, visibility, regional air pollution and human health. Aerosols are very complex in structure, can contain thousands of different chemical compounds within a single particle, and need to be analysed for both size and chemical composition, in real-time or off-line applications.
Air pollution measurement is the process of collecting and measuring the components of air pollution, notably gases and particulates. The earliest devices used to measure pollution include rain gauges, Ringelmann charts for measuring smoke, and simple soot and dust collectors known as deposit gauges. Modern air pollution measurement is largely automated and carried out using many different devices and techniques. These range from simple absorbent test tubes known as diffusion tubes through to highly sophisticated chemical and physical sensors that give almost real-time pollution measurements, which are used to generate air quality indexes.
A cascade impactor measures the reach range of a particulate substance as it moves through an opening with the use of aerosol. Cascade impactors are strictly measurement-related devices. In addition to measuring the range of substances moved through an opening by aerosol, the impactor can also be used to determine the particle size of the distributed substance. A cascade impactor collects its samples in a graduated manner. This allows the user to identify the sizes of the substance particles as the particles are distributed from the propellant aerosol source. When the aerosol substance is distributed into the cascade impactor, the substance enters a series of discs designed to collect solids and different particulate matter. The substance is thus collected as it passes through the disc series. Each disc is set in sequence with both the prior and the previous disc. The size of the discs is graduated as well, to properly determine the size of the particulate matter at each stage of the impactor.
Occupational dust exposure occurs when small particles are generated at the workplace through the disturbance/agitation of rock/mineral, dry grain, timber, fiber, or other material. When these small particles become suspended in the air, they can pose a risk to the health of those who breath in the contaminated air.
The health and safety hazards of nanomaterials include the potential toxicity of various types of nanomaterials, as well as fire and dust explosion hazards. Because nanotechnology is a recent development, the health and safety effects of exposures to nanomaterials, and what levels of exposure may be acceptable, are subjects of ongoing research. Of the possible hazards, inhalation exposure appears to present the most concern, with animal studies showing pulmonary effects such as inflammation, fibrosis, and carcinogenicity for some nanomaterials. Skin contact and ingestion exposure, and dust explosion hazards, are also a concern.
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. TEOM-based devices have been approved by the U.S. Environmental Protection Agency for environmental air quality monitoring, and by the U.S. Mine Safety and Health Administration for monitoring coal dust exposure for miners to prevent several respiratory diseases.
Workplace exposure monitoring is the monitoring of substances in a workplace that are chemical or biological hazards. It is performed in the context of workplace exposure assessment and risk assessment. Exposure monitoring analyzes hazardous substances in the air or on surfaces of a workplace, and is complementary to biomonitoring, which instead analyzes toxicants or their effects within workers.
