WHAT IS ACTIVATED CARBON?
Each grain of activated carbon or charcoal is, in effect, a molecular sponge with a tremendous area of internal surface in passageways so small that they cannot be seen by an optical microscope. It is this surface that adsorbs and retains the odors, vapors, and gases. Even though the deposit of adsorbed contaminant is only one or a few molecules deep, the amount of material adsorbed can be surprisingly large because of the great internal surface. The grains in one pound of activated carbon have an internal surface of about five million square feet.
It has been known since ancient times that carbon has the power to purify air and water. Ordinarily carbon, as normally produced, possesses to a slight degree the power to adsorb and hold contaminating materials. But by high temperature steam activation, the process employed in the manufacture of activated carbon, the adsorption capacity is increased a hundredfold or more. New important methods of utilization as a total purification treatment or as part of a treating system have been developed. Activated carbon types are now available which have low air resistance, high adsorptive capacity, and other characteristics especially suited to the treatment of industrial waste gases. For many problems, standard commercially available activated carbon filter cells provide effective and economical solutions.
Everyone has had some contact with activated carbon. Its use in gas masks, for water purification, and for deodorization is well known. The public is now learning about activated carbon through some of its new personal and household uses. Many are using filter tip cigarettes which contain activated carbon. Disposable activated carbon filters are being widely used in forced air furnaces and air conditioners. The public knows from popular articles that activated carbon helps the atomic submarines to stay under water for weeks or months and manned space capsules to stay in orbit for many days. Many have had contact with activated carbon in its industrial applications, and know of the beneficial ways it can be used.
ACTIVATED CARBON
ACTIVATED CARBON IS LIKE A MOLECULAR MAGNET. It is a form of carbon in which we create millions of tiny holes, which form an internal structure of interconnected capillary passages not much larger than the molecules that it adsorbs. Although activated carbon can be made from a variety of raw materials and by different methods of processing, we carefully select the material and processes that produce the combination of properties required for maximum effectiveness in each of its many applications.
Adsorption is commercially useful, because it can be used to remove impurities from air, gas and liquid mixtures even though the contaminants are present only in trace amounts.
ADSORPTION
Adsorption is a physical action based on molecular forces. When an air, gas or liquid containing impurities is brought into contact with it, the activated carbon attracts and holds the impurities on its internal surfaces. The degree of adsorption depends on the relationship between the carbon pore structures and the size and shape of the contaminating molecules.
A tremendous surface area is contained within a small volume of activated carbon. For example, the area in one quart (about one pound) of some types of carbon is as high as 9 million square feet. This makes absorption practical and one of the most effective methods of positive air purification known. Air purified with activated carbon is actually purer than much of the outside air we normally consider fresh and sweet.
PURIFICATION
Gas – Air and gases are purified by removing organic and inorganic contaminants in high and very low concentrations as small as one per billion.
Liquid – Activated carbon removes unwanted tastes, odors, colors, chlorine, and a wide range of contaminants from water and other liquids. Washed grades are available for high purity requirements of medicinal, food and beverage applications.
RECOVERY
Air – Contaminated air is recovered and recirculated at less cost than heating or cooling outside air. This improves indoor environment, stops pollution by exhaust air, improves neighborhood relations.
Solvents – Valuable solvents are recovered from the air at a fraction of their original cost. This helps improve products by making the best solvents economical to use.
Reclamation – Dry cleaning solutions, plating baths and degreasing solvents are reclaimed for reuse. By-product liquids, gases and waste products are recovered for resale, reuse of simplified disposal.
CATALYSIS
Catalyst – Activated carbon is used to catalyze a variety of specific chemical reactions. Activated carbon will decrease in catalytic activity only when exposed to large quantities of high molecular weight materials and is not readily poisoned by the usual contaminants.
Catalyst Support – Activated carbon’s high adsorption capacity holds more metallic salts than other supports. Its large internal structure also effectively concentrates reactants and promotes catalysis.
SEPARATION
Concentration – The high adsorptive capacity of activated carbon is used for concentrating many types of substances present in dilute form in gases and liquids. Carbon adsorption is often faster and more economical than concentration by evaporation, chemical reaction, ion exchange and other methods.
Fractionation – Activated carbons have adsorbent capacity for a wide range of molecular sizes and shapes. By proper selection of carbon types and operation of adsorptive equipment, it is possible to fractionate molecules, thereby separating one type or size from another. In specific cases, adsorption or chromatographic techniques will achieve a degree of separation usually not possible with other methods.
ADSORPTION EQUIPMENT FOR AIR POLLUTION CONTROL
Adsorption is a physical phenomenon which permits the removal of contaminants from gases and liquids. These contaminants can be reduces to as low a level as desired. The molecules of the contaminant are trapped and held by the internal surface of the adsorbent. A number of commercial materials have the property of adsorption, including activated carbon, silica gel, activated alumina, molecular sieves, and certain clays.
This discussion relates primarily to activated carbon since it is the best known and most effective adsorbent for air pollution control.
MANUFACTURE AND SELECTION OF ACTIVATED CARBON
Activated carbon is prepared from nut shells, wood, coal, or other carbonaceous material, and activated by the use of steam at high temperature to burn away part of the carbon substance in a definite pattern to give a large amount of internal surface, thereby imparting to the carbon the property of adsorption. We start with a crude carbon which has only a few pores or holes, due to the original structure of the carbonaceous material. The rest of the carbon is relatively solid. During activation, the black grains become lighter in weight and acquire an internal pore structure having a large surface. The more highly activated the carbon, the greater the surface and pore volume.
The selection of the right grade to use depends on such factors as general class of application, type and concentration of contaminants, efficiency required, resistance to liquid or gas flow, heat transfer, thickness of bed used, method of support for carbon bed, and operating conditions. The final selection to determine the best type and mesh size to use is ordinarily based on laboratory tests. It may be necessary to compare several grades. We can help you make the selection.
HOW ACTIVATED CARBON IS USED FOR POLLUTION ELIMINATION
The basic principle for using activated carbon in the solution of adsorption problems is simple. Either move the fluid (gas or liquid) through the carbon or move the carbon through the fluid. The carbon can be used in either a fixed or moving bed. It can be contained in standard filter cells or packed into adsorber vessels or towers.
The pollutants are adsorbed by the carbon grains which increase in weight by the amount they adsorb. This continues until the capacity of the carbon is reached and then the pollutants are no longer adsorbed but are passed through the bed. At this point or before, the carbon must be replaced or reactivated. Activated carbon saturated with pollutants can be reconditioned in high temperature steam reactivating furnaces similar to those employed in the original manufacture of the carbon. In some cases, it is technically possible and economically feasible to desorb all or part of the pollutants with steam, direct heat, or solvent washing as part of the adsorption/desorption process (Solvent Recovery).
At ordinary temperatures the so-called permanent gases are adsorbed to a minor extent compared with those which have boiling points at room temperature or above. The high molecular weight materials under certain conditions will displace smaller molecules which were already adsorbed in activated carbon. Suppose, for example, we pass air containing butane, pentane, and hexane through a bed of activated carbon. The carbon will remove all three of the hydrocarbons until a breakthrough is reached, at which point some of the butane starts to come through, but the other hydrocarbons are completely adsorbed. If the adsorption is carried on for a sufficiently long time, the carbon will contain mainly hexane with only small amounts of butane and pentane.
The initial efficiency of a fixed bed is a function of particle geometry and contact time. For our purposes, contact time is the bed volume in feet divided by the CFM; times 60. This is a standard concept of contact time and is useful for our purposes. As a rule-of-thumb, when the contact time is doubled, the loss (100 minus the efficiency) through the carbon bed is cut to one-tenth. Suppose we have a carbon bed with a volume of a 8 f^3, CFM of 200, and an initial efficiency of 99%. The contact time is 2.4 seconds. If we double the contact time, making it 4.8 seconds, by either cutting the CFM in half or by doubling the depth, we will reduce the loss from 1% to a tenth of 1%, making the initial efficiency 99.9%. If, on the other hand, we cut the contact time in half (to 1.2 seconds), by either doubling the CFM or cutting the thickness in half, we increase the loss from 1% to 10%, making the efficiency 90%. In general, contact time for gas treatment operations vary from 1/10 to 10 seconds.
The initial efficiency does not measure the capacity of the ed to break-through or saturation. These depends on the rate of contaminant flow, the mass of the carbon, and adsorption characteristics of the carbon. The lower the amount of contaminants to be removed per minute, the greater the weight or volume of the carbon, and the higher the adsorption capacity of the carbon; the longer will be the service life of the bed.
For fixed bed installations, which handle large quantities of gas or liquid, and where then carbon layers can be used because a short contact time is suitable, an arrangement of vertical beds between screens or cylindrical beds may be used to advantage. For the continuous operation of fixed bed systems, two or more vessels are required together with the necessary interconnecting valves to switch the flow of material being treated and, in some cases, the flow of the desorbing fluid.
Contact with oxygen, chlorine, and certain other gases at high temperatures should be avoided. Carbon is combustible, but not easily ignited. In the absence of a blast of air, hot activated carbon supports combustion with difficulty and under some conditions will go out on its own accord. Activated carbon is not ignited by high velocity air at temperatures of 300˚F or less. With low air velocities, somewhat higher temperatures can be employed.
In problems where combustible materials are adsorbed from air, it is generally advisable to handle mixtures that are below the lower explosive limit. If they are more concentrated, it may be desirable to dilute them with additional air of inert gas. This adds to the size of the system, but makes it safer.
If the concentration of contaminant is high, it may be best to remove it in several adsorption stages. For example, if a contaminant is present in a concentration of one part per million and it is desired to reduce it to less than one part per billion, treatment by passing through a bed of activated carbon two or three feet thick may suffice. If, however, the contaminant is present in a 1% concentration and it is desired to reduce it to less than one part per billion, it might be well to do this in two separate stages.
Activated carbon is generally used as a concentration method so that vapors can be disposed of in a concentrated form by other means such as burning or reuse in a process. There are a few exceptions where activated carbon is the carrier for disposal by dumping in the solid form or by flushing down the sewer, or where the carbon destroys the contaminant by catalysis.
From an operating cost point of view the contaminants should be eliminated either as close as possible to the polluting source or as close as possible to where the air is used. By treating the air close to the source, it is purified in the most concentrated form and the total load of waste materials can be eliminated with the least expense. If the air is treated close to the use, it is necessary to purify only that portion actually used (removing only a small total amount of impurities), but the surrounding atmosphere is contaminated. To do anything in between these two extremes would mean purifying thousands of cubic yards of the atmosphere and in most cases would be impossible. Activated carbon is an excellent means of removing contaminants either at the source where they are concentrated or at the point of use where they may be dilute.
The continued success of an adsorption system depends on the regeneration of recharging the system. This can be done several ways as follows:
1) Remove carbon in bulk
a) reprocess on site
b) return to factory
c) throw away and replace with new
2) Remove all cells
a) refill on site
b) return to factory for refill and servicing
c) use throwaway type cells
3) Regenerate in-place
a) steam, direct heat, recirculating vapor
b) reduce pressure
c) extract with solvent
VERSATILITY OF ACTIVATED CARBON
Activated carbon is a universal absorbent. It has the ability to remove from air or gas and hold within its capillary pores almost all types of objectionable gases and vapors. They are taken up because of the property of adsorption; the carbon removes and retains within its microscopic porous structure almost all volatile materials, whether they are chemicals, solvents, or mixtures of odor-causing substances. The only gaseous materials which it will not adsorb well are low molecular weight gases such as oxygen, nitrogen, carbon monoxide, and carbon dioxide. Even in this range, some compounds such as ammonia are adsorbed in reasonable quantities and adsorption is a satisfactory way of eliminating them if they do not constitute the major contaminating load. For some low molecular weight reactive gases impregnated carbon can be used to combine adsorption and chemical reaction.
The type of application where activated carbon gives the most outstanding performance is the removal of organic vapors with boiling points above room temperature. These include the essential oils, solvents, organic intermediates, organic waste materials, in fact most of the odors that exist. Of these, activated carbon takes up a quantity equal to about one-third of its own weight and will adsorb the vapors completely from concentrations varying from pure vapor down to a level so low that it can be neither smelled nor measured.
Activated carbon performs efficiently whether the contaminant concentration is high, low, or variable. No other elimination method will work with high efficiency on concentrations which may be as low as a fraction of one part per million or billion. The same simple system can be used for hundreds of such problems.
Complete treatment with carbon is a widely used process
method. Pass almost any exhaust mixture
through a deep bed of activated carbon and everything of an obnoxious nature is
removed. You don’t necessarily have to
know what the pollutant is to remove it with activated carbon; it just does the
job. For example, we do not know exactly
what
Activated carbon can be used to remove particulate material in conjunction with gas or liquid adsorption in certain instances. For this purpose it is necessary to use a rather deep bed compared with that required for adsorption only. This procedure is used in removing oil from compressed air, part of it is present as vapor and part as smoke. Both can be removed if a deep bed of carbon is used. In the brewing industry, it is common practice to use activated carbon to completely decontaminate air, that is, remove all vapors and harmful particulate matter, including bacteria. In such a case, a very deep carbon bed is employed (about 10 feet) and experience has shown that this does a good job of complete purification.
Because of its simplicity, activated carbon adsorption can be used separately on each of a battery of fume emitting sources. This saves piping and other expenses. For example, carbon can be used in convenient adsorption traps to eliminate contaminants being discharged from tank vents; there are no moving parts and the trap can breathe freely in either direction. In addition to preventing contaminants from leaving the tank to the atmosphere, it prevents the contamination of the tank contents from impurities which may be in the air.
With this type of venting, tanks can be placed inside of buildings in cases where it would be more convenient. On submarines, the tanks which hold waste materials are equipped with carbon vents. If this were not done, there would be a serious odor problem. Also, on submarines, especially the atomic subs, carbon is used to purify the air used from ventilation. This permits the submarines to stay down for more than a month using the same air over and over. The CO2 is removed by usual methods, oxygen is added, and the carbon takes out the other contaminants.
ACTIVATED CARBON IN CONJUNCTION WITH OTHER PURIFICATION
SYSTEMS
Although activated carbon will remove from exhaust air almost every type of contaminating substance, there are cases where the cost of operation can be reduced by removing part of the load ahead of the carbon beds by filtering or scrubbing. For example, it may be feasible to remove a major portion of the heavy contaminating load by scrubbing the air with water in a packed tower. This may save carbon cost, and result in more economical operation of the system.
Activated carbon may be used as a final purification step in conjunction with a system already installed. For example, if a company is using electrostatic precipitation and a caustic scrub to clean up its exhaust gases, and if the efficiency of the system is not 100%, it may be possible to complete the job adding carbon filters.
An excellent combination treatment method consists of two basic steps, scrubbing the gas with water and activated carbon adsorption. The water removes particulate matter, some of the vapor if the concentration is high, and cools the gas if it’s hot. The carbon removes any remaining vapors. Additional non-contaminated air is added to the stream after the water scrubber so that the air entering the carbon absorber is not completely saturated. This method is a logical answer to many pollution problems.
PERFORMANCE AND COST
Depending on the type of service, an activated carbon bed may be from ½” thick with 30 to 50 feet per minute face velocity to several feet in thickness with velocity in the range of 30 to 200 feet per minute. A carbon filter might last for a year or more in dilute and intermittent service, or might have to be desorbed as often as once an hour where contaminants are being recovered. The capacity of activated carbon for repeated adsorption and desorption is tremendous. When removing easily desorbed compounds it can operate on one hour cycles for years. The installation cost of activated carbon treatment may vary from about $60.00 per thousand cfm to $25,000 per thousand cfm. In the higher brackets, part of the cost may be in-place desorption equipment which produces values that offset the cost of treatment. The operating cost per pound of contaminants removed may vary from a fraction of a cent per pound for intermittent standby service on dilute concentrations. These are wide limits, but activated carbon has wide application.
Activated carbon should be considered either as a complete solution or as a treatment step for most pollution control problems. Although it will not be the best solution in all cases, it will often be the best alternative. Its use is increasing as its amazing capabilities become more widely known.
NEW EMPHASIS ON
INDOOR AIR QUALITY
ACTIVATED CARBON AIR PURIFICATION FOR HEALTH BENEFITS
Activated carbon adsorbs smog and organic vapors from polluted air. Wherever gaseous air contaminants produce irritation of the eyes, nose, throat, or lungs, proper use of the adsorbent may relieve such ailments in many individuals. Where irritations or allergic reactions are of concern, activated carbon is useful in removing odors that may arise in spaces that are shut tightly to keep out the particles.
Activated carbon effectively removes odors and “stuffiness”, which may produce headaches and psychic distress in some individuals. It is also useful in hospitals and sick rooms to remove odors caused by diseases, incontinence, and medication.
Activated carbon removes from air practically all contaminants present in the form of gas or vapor, including odor, smog and toxic gases. The airstream passes through an activated carbon filter, where the contaminants are removed and the air with all of its oxygen is recovered in pure form. To remove dust and pollen, one of the standard dust-arresting filters can be used on conjunction with activated carbon. The combination of activated carbon and dust filters is used wherever the removal of both vapors and particles is desired.
People who suffer from irritation of the eyes, nose, throat and lungs, have reported relief through the use of activated carbon. Whether the irritant is an odor, vapor, smog, smoke or a combination, activated carbon equipment may give complete or partial relief.
Activated carbon has been used for years in hospitals. It effectively removes the odors of disinfectants, medicines, and chemicals, as well as other odors found in hospitals, doctor’s offices, and morgues.
Contamination of air in a living or working area can come from the outside or inside. Outside air contains smoke, smog, industrial waste products, automobile exhaust fumes, dust and pollen. Indoor contamination can come from patients, personnel, cooking, pets, tobacco, perfumes, and cleaning compounds. All of these odors can be effectively removed with activated carbon equipment.
Smog can be completely removed by activated carbon. The irritant vapors in cigarette smoke can be taken from the air by carbon adsorption. Activated carbon is not a cure-all, but experience shows that in a high percentage of cases where there are definite irritants, positive benefits have been achieved.
BUILDING CODE
REGULATIONS OF RECIRCULATION OF AIR
THROUGH ACTIVATED
CARBON
Most municipal building codes require minimum amounts of outside air for ventilation of occupied spaces. However, some also provide for the elimination of all or part of such requirements wherever room air is recirculated through properly installed and maintained odor-removing devices using activated carbon. An increasing number of local authorities allow the substitution of activated carbon purified air for outside air, even though not provided for in their codes, by interpreting purified room air to be the equivalent of outside air for ventilation purposes.
Public health authorities long ago decided that building codes should provide for minimum standards of ventilation. To this end, they usually specified, often by an arbitrary rule of thumb, a minimum window area per occupant or per unit of floor area. As engineers developed mechanical means of ventilation, architects sought to use it in lieu of windows and other openings. At first, the codes were not changed. Buildings had to have so many windows, whether they were actually used or not. Eventually, the codes were altered to allow mechanical supply of a specified amount of air from outside.
In order to make the minimum requirements less arbitrary, health authorities conducted tests to determine how much fresh air people really need. It was found that discomfort could be caused by excessive temperature, air stillness, humidity, smoke, dust and odors. Therefore, recirculation of room air through filters and control of temperatures and humidity could reduce the requirements for outside air, a certain amount of which was still considered necessary to supply oxygen and to remove carbon dioxide and odors.
Next, it was found that plenty of oxygen and low enough concentrations of carbon dioxide would exist in all but the most tightly sealed spaces, owing to normal infiltration of air through doors and building joints. The ultimate limit in the reduction of outside air requirements was thus dictated by the need to eliminate odors from human occupancy. New minimums were drawn up that were based upon the amount of outside air needed to dilute odors to their threshold level, or at least to a level that would not produce general discomfort.
ODOR REMOVAL BY ADSORPTION: We can now remove odors by adsorption with activated carbon and eliminate mechanically supplied outside air. The technical capability of doing this has been proven. The only limiting factor is rigid interpretation of antiquated building and health codes.
As was often the case with other forms of air treatment, activated carbon purification was first installed not so much to eliminate outside air as to improve upon conditions. (The code requirements are conservative, as far as health is concerned, but they may permit odor conditions that are less than ideal.
COMMUNITIES ACCEPTING ODOR ADSORPTION: The demand for reducing or eliminating the requirements for outside air has been strongest where the cost savings could be the greatest, generally where the climate may be hot or cold. The quickest changing of the codes has been in those places and, also, in localities where the air out of doors may be obviously inferior to the air inside a conditioned space. In some smog-ridden areas, codes now permit 100 percent recirculation. Where new codes have not been adopted, inspectors sometimes rule that air recirculated through properly installed and maintained filters of activated carbon, is in effect, outside air (as far as interpretation of the code is concerned). Where inasmuch as other sections of the code require a minimum number of doors, fire exits, special vents.
Many localities have accepted the recommendation of the
International Conference of Building Officials, which allows 100 percent
recirculation, or the
Where the use of activated carbon is contemplated and the situation is properly explained to the code enforcement authorities, the requirement for outside air is usually waived. Members of the American Society of Heating, Refrigeration and Air Conditioning Engineers usually accept the principle of odor adsorption as giving in the ASHRAE Guide and Data Books.
ACTIVATED CARBON
AIR PURIFICATION
CLEAN ROOMS
Modern technology requires many production facilities that must be free of virtually all dust, lint, smoke particles, and corrosive or otherwise contaminating gases and vapors. Such facilities are often called “clean rooms” or “white rooms”. They may be required for the production, testing, or use of such delicate or sensitive equipment as missile guidance packages, electronic computers, micro chemical balances, optical devices, and space vehicle components.
INCREASE IN CLEAN ROOMS: More and more attention is being given to contamination control for at least five reasons (1) the precision and sensitivity of the products needs to be greater (2) the reliability required is much greater (3) smaller and lighter products are needed (4) more items of that type are being manufactured (5) air pollution is increasing.
PARTICLES, TEMPERATURE, HUMIDITY
The initial objectives for clean rooms were the exclusion of particulate matter and the control of humidity and temperature. Particulate matter may be abrasive and may clog small openings and delicate electrical contacts. High or variable humidity may promote rusting and corrosion of metals, plus swelling, cracking and distortion in other materials. Variations in temperature may throw both the product and the tools for its manufacture out of alignment or balance.
GASES AND VAPORS
Recently, contamination from corrosive, toxic, and reactive gases and vapors has been recognized as a growing problem; therefore, activated carbon is being used increasingly in contamination controlled facilities. Some authorities believe they cannot have a real clean room without it. Activated carbon adsorbs most of the gases and vapors that may interfere with clean room operations. In addition, it can be used to reduce the cost of other types of air treatment for clean rooms by permitting as much as 100% recirculation of the expensive, treated air. The gases that may cause corrosion include sulfur oxides, hydrogen sulfide, mercaptans, nitrogen oxides, hydrochloric acid, salt spray, halogen vapors, refinery gases, smelting gases and smog. Other gases and vapors also may interfere with clean room operations under special conditions. Some products can be contaminated by ordinary odors and may have to be rejected on that account. In some cases, activated carbon is used when it is not known what the troublesome contaminants are. Activated carbon removes all organic gases and vapors and many inorganic types and is an excellent safety precaution to eliminate any extraneous compounds which might affect the work being done.
CARBON EFFICIENCY AND CAPACITY
Activated carbon has high efficiency for the removal of all such gases and vapors. It also has high capacity for most of them, including asphalt fumes, carbon didulfide, chlorinated hydrocarbons, tobacco smoke vapor, smog and odors. The gases and vapors for which activated carbon has a low capacity may need special consideration. They include some freons, formic acid, sulfur dioxide, some amines, some mercaptans, arsine, stibine, carbon dioxide, nitric acid, ammonia and formaldehyde. Standard carbon filters may be employed directly for their removal if the total amount of contaminant is small, that is, if they are found either in low concentrations or in moderate concentrations for a limited period of time. Special techniques, such as impregnation of the carbon with additives, increase absorptive capacity for some contaminants. Another technique that can be used in some cases is in-place regeneration of the carbon.
HOW WELL WILL ACTIVATED CARBON WORK FOR YOU?
Acetaldehyde 2
Acetic acid 4
Acetic anhydride 4
Acetone 3
Acetylene 1
Acrolein 3
Acrylic acid 4
Acrylonitrile 4
Adhesives 4
Air-Wick 4
Alcoholic beverages 4
Amines 2
Ammonia 2
Amyl alcohol 4
Amyl ether 4
Amylacetate 4
Anesthetics 3
Aniline 4
Animal odors 3
Antiseptics 4
Asphalt fumes 4
Automobile exhaust 3
Bathroom smells 4
Bleaching solutions 3
Body odors 4
Borane 3
Bromine 4
Burned flesh 4
Burned food 4
Burning fat 4
Butadiene 3
Butane 2
Butonone 4
Buty acetate 4
Butyl alcohol 4
Butyl ether 4
Butyle cellsolve 4
Butyle chloride 4
Butylene 2
Butyne 2
Butyraldehyde 3
Butyric acid 4
Camphor 4
Caprylic acid 4
Carbon dioxide 1
Carbon disulfide 4
Carbon monoxide 1
Carbon tetrachloride 4
Carbonic acid 4
Cellosolve 4
Cellosolve acetate 4
Charred Materials 4
Chclohexene 4
Cheese 4
Chlorine 3
Chlorobenzene 4
Chlorobutadiene 4
Chloroform 4
Chloronitropopane 4
Chloropicrine 4
Cigarette smoke odor 4
Citrus and other fruits 4
Cleaning compounds 4
Combustion odors 3
Cooking odors 4
Corosive gases 3
Creosote 4
Cresol 4
Crontonaldehyde 4
Cyclohexane 4
Cyclohexanol 4
Cyclohexanone 4
Dead animals 4
Decane 4
Decaying Substances 4
Deodorants 4
Detergents 4
Dibromethane 4 4
Dichlorobenzene 4
Dichlorodifluoromethane 4
Dichloroethane 4
Dichloroethyl ether 4
Dichloroethylene 4
Dichloromonofluormenthane 3
Dichloronitroethane 4
Dichloropropane 4
Dichloroterafluoroethane 4
Diesel funes fumeodor 4
Diethyl ketone 4
Diethylamine 3
Dimethylaniline 4
Dimethylsulfate 4
Dioxane 4
Dipropyl ketone 4
Disinfectants 4
Elhane 1
Embalming odors 4
Essential oils 4
Ether 3
Ethyl acetate 4
Ethyl acrylic 4
Ethyl alcohol 4
Ethyl amine 3
Ethyl benzene 4
Ethyl bromide 4
Ethyl chloride 3
Ethyl ether 3
Ethyl formate 3
Ethyl mercaptan 3
Ethyl silicate 4
Ethylene 1
Ethylene chlorhydrin 4
Ethylene dichloride 4
Ethylene oxide 3
Eucalyptole 4
Exhause fumes 3
Film Processing Odors 3
Fish odors 4
Floral scents 4
Fluorotrichloromethane 3
Food aromas 4
Formaldehyde 2
Formic acid 3
Fuel gases 2
Fumes 3
Gangrene 4
Garlic 4
Gasoline 4
Heptane 4
Hexana 3
Hexylene 4
Hexyne 3
Hoptylene 4
Hospital odors 4
Household smells 4
Hydrogen 1
Hydrogen bromide 2
Hydrogen chloride 2
Hydrogen cyanide 2
Hydrogen iodide 3
Hydrogen selenide 2
Hydrogen sulfine 3
Incense 4
Indole 4
Industrial wastes 3
Iodine 4
Irritants 4
Isophorone 4
Isoprene 3
Isopropyl acetate 4
Isopropyl alcohol 4
Isopropyl ether 4
Kerosene 4
Kitchen odors 4
Lactic acid 4
Lingering odors 4
Liquid fuels 4
Liquor odors 4
Lodotorn 4
Lubricating oils and greases 4
Lysol 4
Masking agents 4
Medical odors 4
Melons 4
Menthol 4
Mercaptans 4
Mesityl oxide 4
Methane 1
Methycyclohexanol 4
Methyl acrylate 4
Methyl alcohol 3
Methyl bromide 3
Methyl buty ketone 4
Methyl cellosolve 4
Methyl cellosolve
acetate 4
Methyl chloride 3
Methyl chloroform 3
Methyl ether 3
Methyl ethy ketone 4
Methyl formate 3
Methyl isobuty ketone 4
Methyl mercaptan 4
Methylacetate 3
Methylcychlohexane 4
Methylcyclohexanone 4
Methylene chloride 4
Mildew 3
Mixed odors 4
Monochlorbenzene 4
Monofluorotrichloromethane 4
Moth balls 4
Naphthalene 4
Naptha (coal tar) 4
Naptha (petroleum) 4
Nicotine 4
Nitric acid 3
Nitro benzenes 4
Nitroethane 4
Nitrogen dioxide 2
Nitroglycerine 4
Nitromethane 4
Nitropropane 4
Nonane 4
Octailene 4
Octane 4
Odorants 4
Omons 4
Organic chemicals 4
Ozone 4
Packing house odors 4
Paint and redecorating odors 4
Palmitic acid 4
Paper deteriorations 4
Paradichlorobenzene 4
Paste and glue 4
Pentane 3
Pentanone 4
Pentylene 3
Pentyne 3
Perchloroethylene 4
Perfumes, cosmetics 4
Persistant odors 4
Perspirations 4
Pet odors 4
Phenol 4
Phoagene 3
Pitch 4
Plastics 4
Pollen 3
Popcorn and candy 4
Poultry odors 4
Propane 2
Propionaldehyde 3
Propionic acid 4
Propyl alcohol 4
Propyl chloride 4
Propyl ether 4
Propylacetate 4
Propylene 2
Propylmercaptan 4
Propyne 1
Putrefying substance 3
Putrescine 4
Pyridine 4
Radiation products 2
Rancid oils 4
Reodorants 4
Resins 4
Ripening fruits 4
Rubber 4
Sauerkraut 4
Sewer odors 4
Skatole 4
Slaughtering odors 3
Smog 4
Smoke 4
Soaps 4
Solvents 3
Sour milks 4
Spoiled food stuff 4
Stale odors 4
Stoddard solvent 4
Stuffiness 4
Styrene monomer 4
Sulfur dioxide 2
Sulfur trioxide 3
Sulfuric acid 4
Tar 4
Tarniching gases 3
Tetrachlorethylene 4
Tetrachloroethane 4
Theatrical makeup odors 4
Tobacco smoke odor 4
Toilet odors 4
Toludine 4
Toluonn 4
Trichlorethylene 4
Trichloroethane 4
Turpentine 4
Urea 4
Uric acid 4
Valeric acid 4
Valericaldehyde 4
Varnish fumes 4
Vinegar 4
Vinyl chloride 3
Waste products 3
Wood alcohol 3
Xylene 4
Index # Meaning
4.
Carbon works at High Capacity for all materials in this category.
3. Carbon
works at satisfactory capacity for all materials in this category.
2. Carbon
may or may not give satisfactory capacity for these materials.
1. Carbon
absorption is low for these materials.
Activated carbon cannot normally be used to remove these materials.