Air pollution from industries is constantly emerging as a big threat to health of individuals as well as environment. Smoke and pollution from chemical and pharmaceutical industries is posing a serious threat to human life. Inefficient handling of hospital wastes contribute to total viral load of communicable diseases. In fact, according to a recent survey more than 50 per cent allergies in community are acquired from nosocomial infections of typical environment in government hospitals, of which 90 per cent result in major disease.
The most apparent effect of air pollution is skin allergies leading itching, inflammation, neurological problems like varicose veins, respiratory problems of upper respiratory tract like coryza & bronchitis, which worsens with consumption of tobacco and other similar products. Many patients suffering from air borne allergic diseases produce productive cough and show possible signs of tuberculosis or asthma. Such common allergic diseases add to psychological factors like stress, anxiety, phobia and cardiac abnormalities like dysrhythmias.
Air pollution increases load of toxic gases in the atmosphere such as Oxides of Nitrogen (NOx), Oxides of Sulfur (SOx), Oxides of Carbon (COx), Chlorinated compounds and Inert gases. Air pollution concerns deepen when we speak about quality of indoor air. Tobacco smoke, volatile organic compounds (VOCs), aromatic vapors, phenolic vapors, methane, ammonia, and other incense gases are common in environment of pharmaceutical industries.
Communicable micro-organisms, toxins and viruses in hospital environment coupled to HVAC systems only add to poor quality of air we breathe indoors. In fact, indoor hospital air is 100 times more polluted with infectious agents as compared to environment outside with garden refuge free of medical wastes. After years of research with Atlanta HealthcareTM we came up with innovative solution in 2008 for deployment of air purifiers to improve the quality of air we breathe indoors.
Air purifiers by Atlanta HealthcareTM primarily focus to impart good quality of air rich in oxygen, free from dust, particulates and viruses to minimize impact on health. We focus on quality of air hygiene to minimize ‘illness’ and enhance physical and mental state for optimal metabolic efficiency to enable complete well-being of an individual. Each year about two million people develop respiratory allergy and air pollution estimates to cause death of 1.3 million people worldwide due to pneumonia, asthma, tuberculosis, cystic fibrosis or lung cancer in children and adults. Particulate matter of size greater than 10 micrometer (µm) is capable of penetrating bloodstream from lungs to cause respiratory disease. Occupational health concerns involving safety and well-being of the person due to poor quality air is of paramount importance.
Air filtration: Filtration is the most common and widely used physical process to separate constituents from a flowing stream of fine solids, water or gas through a membrane. Membrane filtration is a simple process easy to validate for mixture of substances in air or water. Membrane acts as a physical barrier comprising of small holes or pores that allow selective passage of flowing components of air/water whilst retaining larger unwanted molecules. Selectivity expresses parameter of separation or retention and Productivity expresses membrane dependent flux in typical membrane filtration process. Pressure gradient is generally applied as a means to force the material through pores of the membrane. Depending upon the range of particles that are to be separated, membrane filtration can be divided into different types such as Microfiltration (MF), Ultrafiltration (UF), and Nanofiltration (NF). Simple air filtration retains dust and suspended particles in flowing stream of air, which otherwise would cluster the process involving air.
Air filtration is one of the simplest processes in air purification systems where membrane filter of different size acts to remove the contaminants from the air. Good quality air purifiers involve number of other techniques that are useful in eliminating harmful odours of volatile and aromatic compounds as well as tobacco smoke and even microorganisms, virus present in air. Air purifies by Atlanta HealthcareTM can be coupled with HVAC unit in hospital, institutional or industrial environment depending upon the air handling unit (AHU) and air handling efficiency required as output from air purification system. It is important for people suffering with asthma or respiratory allergies to breathe pure air hence, a challenge for air purification system to remove airbourne contaminants and DNA damaging particulates.
Filter based air purification systems trap airbourne particles by simple size exclusion (cm, mm, µm, nm) when air is forced to pass through the pores of filter. Different types of filter materials and nanofibers have specific filtration capacity, which are usually coupled to other purification techniques during purification process. A typical cigarette filter is cellulose acetate nanofiber that inhibits fine particles of tobacco, molecular gases and oily tar. Activated carbon acts as a molecular sieve to adsorb volatile chemicals thus can be incorporated with a membrane filter.
The adsorption process is a surface phenomenon that requires change of particulates in gaseous phase to solid phase to establish equilibrium for filtration. Activated carbon due to low cost and ease of availability as compared to other substances is preferred for filtration but usually assists other processes such as HEPA. A typical nanofiber of range 100 nm – 1000 nm produced by interfacial polymerization of electrospun fibers or cellulose nanofibers couples to activated carbon for enhanced catalytic efficiency. Ceramic nanofibers are also used in some cases but finds limited applications. Most widely preferred ceramic nanofiber is electrospun Titanium dioxide (TiO2) whereas Aluminum oxide (Al2O3) or Silicon dioxde (SiO2) may also be used.
Inorganic nanofibers used in filtration processes are electrospun inorganic salts of organometallic compounds subsequently transformed to ceramics by heat treatment. Nanofibers have wide application in filtration of therapeutic compounds and effective in removal of volatile organic compounds (VOCs), microorganisms and viruses. Nanofibers can be coupled to pigments and absorptive materials for enhancement in filtration process as well as impart longevity to fibers. Nanofibers find many applications in vacuum cleaners. Different quality of nanofibers can be obtained from fiber crops, hardwood, cellulose pulp (filter paper) and mercerized pulp. Such material finds intensive applications in air purification systems available commercially and filtration or purification of other biological compounds. Filters are treated with different reagents to impart specific ionic properties. A typical filtration system may utilize many layers of filter to effectively remove dust and other fine gases.
High-efficiency particulate arrestance (HEPA) is specific system for filtering air used in medical facilities, automobiles, aircrafts designed by specific arrangement of nanofibers. US department of energy specify standards for HEPA to remove 99.7% of particles of size ranging 0.3 µm or more whereas European norms (EN 1822:2009) has a separate criteria for HEPA filters to remove local and total particulate load such as E10, E 11, E 12, H 13, U 17 and so on. Key parameters in design of HEPA filtration is fiber diameter, filter thickness, and face velocity.
HEPA filters are designed to target smaller fine particles that stick to fiber through a combination of three mechanisms namely Impaction, Interception and Diffusion. Air purifies by Atlanta HealthcareTM are effective in retention of particles of size 0.3 µm or 300 nm using combination of mechanisms. HEPA filters are used in combination with Activated carbon for enhanced effectiveness of air purification. HEPA filters are critical in the prevention from airborne bacterial and viral organisms.
Medical equipments systems also incorporate high energy ultra-violet (UV) light units to kill off the live bacteria and viruses trapped by the filter media. Some best-rated HEPA units have an efficiency rating of 99.995 per cent, which assures a very high level of protection against airborne disease transmission. Electrostatic precipitation (ESP) is a filtration mechanism sometimes coupled with HEPA that uses induced electrostatic charged device to removes fine particles, like dust and smoke from a flowing gas and ionizing the gas stream. Some claim ESP is energy efficient process as it reduces consumption of electricity for removal of particulate matter using an electrostatic precipitator.
UV radiations induced by UV lamps effectively sterilize ionized air and remove microbial debris. Polarized media of ESP air cleaners use a combination of electrostatic precipitators, mechanical filters and UV light sterilization. Photocatalytic oxidation (PCO) offers additional prospects to indoor air quality by utilizing catalyst such as TiO2 to accelerate photolysis on adsorbed surface of nanofiber. Nanoparticles of TiO2, together with calcium carbonate neutralize acidic gasses and initiates the decomposition of airborne contaminants at the adsorbed surface. Photocatalysis is an emerging technology in the HVAC industry. Some air purifies are assisted with Ozonators to generate ozone as a byproduct in air purification. Unlike ionizers, ozone generators are intended to produce significant amounts of ozone.
Application of air purifier and consumer concerns
Some common consumer concerns regarding use of air purifiers relates to production of hazardous by-products, level of ozone, noise level, electricity consumption, frequency of replacement of filters or cleaning of plates and in some cases design of air purifier. Most air purifiers for personal use in office/home operation are light in weight and require less handling. Power consumption is low for smaller units and light weight of equipments enables ease to carry from one room to another easily. In United States, some purifiers are certified as Energy Star or rated as energy efficient. Depending upon the extent of use, filter replacement may become necessary once a year. Larger units usually require ceiling installation in specific area and may be coupled to HVAC systems depending upon level of isolation required for operation.
Ozone production is typical for air ionizing purifiers, although high concentration of ozone is dangerous, most air ionizers produce low amounts (0.05> ppm). US Environmental Protection Agency outlines only safe limits of ozonators is permissible in air. Air purifiers reduce concentration of these airborne contaminants and useful for people who suffer from allergies and asthma. Air purifiers are increasingly efficient in capturing greater number of bacterial, virus, and DNA damaging particulates in moist air. Given the vulnerability of habitat and prevalence of infection in community air purifiers are extremely useful for healthcare institutions such as hospitals, clinical, research laboratories, path labs to ensure an environment free from infection.
Air purifiers check levels of bacteria and virus and keep indoor air clean and sanitized for patients as well as general public. Some major industrial applications for air purifiers include removal of dust, toxic fumes, volatile organic matter, oil mist, and harmful odours to enhance performance of production machines as well as industrial occupants working in high precision environment. IT industry has a specific hygiene requirement for regular maintenance of computer operated machines and air purifiers ensure just what is required. Atlanta HealthcareTM air purifiers are ideal for hotels, restraints, gymnasiums, spas, clinics, offices, beauty salons, cinema halls and malls where extensive cleaning is next to impossible and requirement of air hygiene is essential.
(The author is MD of VMG Biotech Consultants, New Delhi)