Air Contaminants - Essay Example

Air contaminants or Air pollutants are particles, gases, and liquids present in the air having harmful chemical properties that affect our health adversely. Liquid or solid contaminants are also termed as ‘particulates’ whereas the rest of the contaminants are in a gaseous state. These air contaminants have been classified into categories which are as follows:

• Criteria Air Pollutants: Ozone, Particulate Matter, Carbon monoxide, sulfur dioxide. Nitrogen Dioxide and Lead. The safe level of exposure can be determined.
• Toxic Air Contaminants: No safe level of exposure. Have over 250 compounds.
• Hazardous Air Pollutants: generally produced as by-products of industries.
• Greenhouse gases: Carbon dioxide, Methane, Nitrous oxide, fluorocarbons, Ozone. They promote climate change.
• Indoor air Pollutants: Mold, Volatile Organic Compounds, Radon, Ozone, Asbestos, Environmental tobacco smoke.

Various methods can be adopted to sample the air pollutants' occurrence and exposure in an environment.

• For Particulates:

Cyclone is used for respirable dust sampling and works on the general principle of centrifugal and gravitational forces to separate aerosols into various-size fractions. It is usually a 10mm cyclone and filter holder assembly attached to a low-flow pump and worn by the worker to obtain personal samples. Further, there are many optical particulate direct reading instruments operating on the principle of the interaction between the particles and visible light such as Transmissometers and nephelometers. The smear technique is also used for identifying sites of contamination. The smear is done using a sterile swab that is rotated on the surface that is to be sampled.

• For Vapors and Gases: Electronic direct reading instruments are used based on the principles of amalgamation, chem.-luminescence, combustion, electrochemistry, infrared spectro-photometry, and photo-ionization. Combustion is a principle used to detect gases and vapors that burn in the presence of oxygen. Carbon monoxide, methane, ethane, and hydrogen are a few gases that can be detected by using this principle. Adsorbent tubes are also used to collect samples containing two sections of adsorbent substances. Sampling bags are used to collect specific gases. These bags are made of different polymeric materials available in different volumes. The phenomena of diffusion across and adsorption by the walls of the bag affect the choice of material for a given substance.
• For Oxygen-deficient atmosphere:

As defined by NIOSH 92004) it is any atmosphere where oxygen is at a concentration below 19.5% at sea level. They are termed life-threatening atmospheres. When oxygen is displaced by carbon dioxide, nitrogen, or the ship's inert gas system or firefighting system or consumed by, ripening fruits, rusting metal, drying paint, or coatings, combustion, or bacterial activities such as oxygen-deficient atmosphere can result. The same can be detected through oxygen indicators, flame safety lamps, and chemical analysis. Oxygen deficiency can be determined in vacuum hot-pressed ferroelectric ceramics using a thermo gravimetric technique as well.

• For Flammable atmosphere:

They are produced by cleaning solvents, paints, flammable fuels, and natural reactions producing methane gas or hydrogen from battery charging of boiler cleaning. Detectors (fixed or portable) are used to continuously monitor the levels particularly where lays possibilities for a leakage into an enclosed space where flammable gases can accumulate. They are sensor units using natural diffusion as the sampling method. Another device is an open-path detector referred to as a beam detector. They consist of a radiation source and a separate remote detector that measures the concentration of gas along the beam’s path.