Permit By Rule (PBR) Application for an Interior Surface Coating Facility

General considerations for operation 

Texas Car Body Repairs shop desires to operate an interior lining (painting) facility. Texas state laws and EPA laws require that such a premise must have an air permit before the construction work begins. Upon completion of the plant, the construction air permit will then be the operational air permit for the premises. The vehicles body repair shop requires a permit application to align the interior surface coating facility to comply with the state and federal air quality laws. The air permit application must meet the air permit criteria as stipulated in the state guidance documents taking into considerations the equipment and chemicals planned for operating the facility. 

Specifications for operating the facility 

The interior liner coating material requires ten gallons coating and two gallons of solvent per vehicle. The lining application will require the use of interior liners to two cars per day each involving five hour per day and four days every week. The internal liner cure heater will use natural gas-fired drying oven. The heater generates 2.1million Btu/hr at maximum 2,500 hours each year. The vehicle lining design will use a cross- draft plenum where the vehicle interior is the spray area. There will be one exhaust fan with 10,000 ft3/ min (CFM). Two filter openings would be included each measuring 2oft 2 . The coating Wv will use VOC content each constituting 2.8 lb/gal of a layer. 1.0 gallon of coating Vm of coating volume will be used. The water content will be 1.0 lb/gal per coat whereas the water density will be 8.34 lb/gal per water. The coating Vw water volume will be computed. The exempt solvent content will be 0.5 lb/gal per coating. The facility will also use 6.64 lb/gal of exempt solvent density. The information on the specification is summarized in a tabular form as shown below. 

Interior Liner	10 gallons	2 gallons of
Coating	coating/vehicle	solvent/vehicle
Material
Vehicle Lining	Apply interior	Work five (5)
Application	liners to two	hours/day and
	(2)	four (4)
	vehicles/day	days/week
Vehicle Lining	Cure interior	Work five (5)
Curing	liners of two	hours/day and
	(2)	four (4)
	vehicles/day	days/week

Interior Liner	Heater fuel	Heater
Cure	the source is	generates 2.1
	Natural gas-	million (MM)
	fired drying	Btu/hr at
	oven	maximum
		2,500 hrs/year
Vehicle Lining	Cross-draft air	Vehicle interior
Design	plenum	is the spray
		area
Exhaust Fan	10,000 ft 3 /min	One exhaust fan
	(CFM)
Air Makeup	5760 ft 3 /min	One air makeup
Unit	(CFM)	unit
Filter	20.0 ft 2 each	Two (2) filter
Openings		openings
Coating WV	VOC content	2.8 lb/gal
		coating
Coating VM	Coating	1.0 gal
	volume
Water Content	Per gal/coating	1.0 lb/gal
Water Density	Per gal/water	8.34 lb/gal
Coating VW	Water volume	Calculation
Exempt-	Per gal/coating	0.5 lb/gal
solvent
Content
Exempt-	Per gal/exempt	6.64 lb/gal
solvent	solvent
Density
Coating Ves	Exempt	Calculation
	solvent volume

Texas Car Body Repairs shop has designed interior coating spray system for the interior of the vehicle allowing it to be coated in a similar manner like new or an extensively damaged car that needs to be restored following a catastrophic even or fire that destroyed its interior. The shop includes a steel structure with a finished concrete floor as well as a paint booth for the cars. The stripped down vehicle will be placed in the spray booth which is open at one end for makeup air. There will be an exhaust chamber for the exhaust air at the other end of the vehicle. A drying operation will start immediately upon completion of the linear application operation. 

Requirements that must be met 

The facility must meet Rule 30 TAC 106.433, TAC chapter 122 Subchapter A, sec 122.10. Similarly, additional data will be gathered on the supplier of the paint, technical datasheet, and material safety data sheet. Such information will aid in the completion of the different calculations and while ensuring compliance with the existing regulations. The data will be helpful in material usage, VOC and exempt –solvent content per gallon of coating, coating, cleanup activities and booth specification. 

VOC and ES Content per Vehicle 

According to Hill & Feigl (1987), hydrocarbons are organic compounds that contain only two elements, i.e., carbon and hydrogen in which case carbon is the base element. Different hydrocarbons include aliphatic, aromatic, halogenated and oxygenated. The understanding the chemical composition of the hydrocarbon, their sources and behavior allows the company to predict, and subsequently engineer indoor air quality using engineering controls. The different types of hydrocarbons are a threat to indoor air quality based on the probability of combining different VOC types resulting in concentrated polluted environments (Godish et al., 2015). Hydrogenated carbons are one of the highly recognized VOCs in air pollution for their bonding characteristics. The can quickly bond with chlorine, fluorine, bromine, and iodine ((Hill & Feigl, 1987; Godish et al., 2015). Indoor air quality can be affected by the creation of narcotic compounds which form an aerosol mist. 

Pollutants from anthropogenic and natural sources are expected in indoor air quality. Quantifying the contaminants, speciation and considering the source of the pollutant is an essential step in air quality engineering strategy. 

VOC calculations 

Using the data from the specifications, the VOC for the component is 2.8 pound per gallon, and the exempt solvent content is 0.5. 

Pounds of VOC for the mixed coating and thinner = (2.8lbVOC/GAL) X 10gal = 28lb VOC per vehicle 

Exempt solvent calculations 

The number of pounds of exempt solvent in the mixed coating and solvent =0.5 X 2gal =1 lb ES per vehicle. The ES content of thinner in the thinner is 0.5 lb/gal. We add the two to get the pounds of exempt solvent in the mixed coating 

=1 lb ES + 0.5 lb ES = 1.5 lb ES 

Dividing the total pounds of exempt solvents by total gallons of mixed coating and solvent to get 1.5 lb ES/5.5gal = 0.273 lb ES per gallon. 

Operational Air Emission Rates 

Hydrocarbons have the potential to form volatile organic compound even in their natural setting. The same hydrocarbons are also used in synthetic products like interior coating material and paint products. Similarly, the hydrocarbons are incorporated into the synthetic product design. The engineers are therefore supposed to forecast and quantify the rate of emission of the VOC from the hydrocarbons that constitute some of the ingredients of the synthetic paint products. Upon completion of the forecasting process of the VOC in a given product, the work system is then evaluated for further impacts on the surrounding ambient air including human health. The air quality engineer should calculate the emission rates in several units of measure to include VOC in pounds per product, hours of work exposure, per year, and even annual tonnage. The engineer is taking something obscure like vapor and converting the VOC to different units for measuring mass. The conversion enables statistical forecasting. The conversion of the pollutants to tangible units like parts per million or parts per billion becomes the primary unit of evaluation for the engineer. They can determine airborne pollutants given that the measures can be expressed as units for mass based concentration for any pollutants that are represented ( Phalen & Phalen, 2013). 

Once the VOC for each costing is determined, the maximum hourly and annual emission rates are determined. The rates are calculated for every coating used at the site. Such computations help in the determination of whether the limits of PBR can be met thus, are useful in the setting of the maximum yearly allowable rates of emission in a permit or in some cases to determine whether the existing regulations apply to the site. The maximum emissions both hourly and annually must be calculated independently. An average hourly emission rate is obtained by dividing the maximum annual emission rate by the yearly operating schedule. If the maximum hourly emission rate is multiplied by the yearly operating schedule, an emission rate that is too large is likely to be obtained. Such values might expose the site to some rules which should not be the case. 

Maximum Hourly and annual emission rate calculations 

The maximum practical hourly application rate must be determined based on the employees or records of the company. Spraying will always be less than the estimates or maximum hourly spray rate provided by the equipment supplier. The maximum amount of each coating to be used throughout the year must also be determined. Based on the calculations of the VOC and ES, the maximum VOC emission rate and maximum exempt solvent emission rate in pounds per hour and the tons per year can be computed as follows. The hourly VOC quantities for the air permit application can be calculated by referencing the case of the coating material. The in this scenario we use two vehicles every day and the 28.0 lbs VOC/vehicle of the coating. The VOC per day will be 28.0 X 2 = 56.0 lbs VOC per day. The VOC per hour is computed by dividing the VOC per day by the 5 hours worked each day. In this case, it will be 56.0/5 = 11.2lbs VOC per hour. 

The next step is to compute the exempt solvent per hour. Based on the SDS information, multiply the computed lbs solvent by two vehicles in a day to obtain 2.0lbs ES. The value is then divided by five hours for each day =2.0 X 1/5 =0.4lbs ES/hour. 

The calculated 56.0lbs VOC/day of the coating is then multiplied by four days for each week =56.0 X 4 = 224.0 lbs VOC per week. The figure is then multiplied by 52 weeks to obtain the value for one year = 224.0 X 52 = 11,648.0 lbs VOC per year. The final step involves multiplying the 11,648.0 lbs VOC/year by 1/2000 lbs or 11,648.0 X 1/2000 =5.82 tons VOC per year. 

The 2.0 lbs ES/day is then multiplied by four days in a week to obtain 8.0 lbs ES/week. The 8.0 lbs are then multiplied by 52 weeks to get 416.0 lbs ES/year. According to TCEQ (2011) on the emission rate averaged over a five hour period, a facility is not allowed to emit over 6 pounds of VOC emissions averaged in a five hour period. Similarly, such a facility is limited to no more than 500 pounds every week for a booth or enclosed worked area. In this case, emission from batch painting should be averaged over a five hour period. The facility meets the PBR emission limit as long as the average is less than 6 pounds per hour. The five hour average in the scenario = 56 lbs VOC per day X 1/5 = 11.2 lbs VOC per hour which is the average over a five hour period. 

According to TCEQ (2011) the potential to emit, the maximum amount of air pollutant generated in a facility should be determined. Potential to emit which is which is the maximum ability of a stationary facility to emit air pollutant under its operational design will be used to obtain a title V operating permit or even for compliance with federal. The maximum hourly and annual emission rates are calculated independently. Care should be taken not to use the average which is obtained by dividing maximum yearly emissions by the annual operations schedule. Additionally multiplying the maximum hourly emission rate by the annual operating schedule produces emission rates that are too high. Such figures will expose the facility to several rules which should not be the case. 

Operational Face and Filter Velocities 

Air pollution can be summarized into four categories, i.e., agricultural, ecological system, structure, and odor. According to Godish, Davis, & Fu, (2015) agricultural pollution incorporates cultivated crops, domesticated animals and natural vegetation. Phytotoxicity which is related to adverse agricultural impact forms the base of documented air quality variables. Heavy metals and particulate matter are some of the highly documented phytotoxins. Other compounds also damage vegetation through photochemical oxidation e.g. ozone. Urban development has led to an increase in the pollution through hydrogen peroxide and peroxyacetyl nitrate (Gurjar, Molina, & Ojha, 2010).The welfare effect of air pollution including poor air quality is caused by the above pollutants that result in Acid rains that lead to soil fertility issues and structural damage of vegetation. A decline in the plant nutrition has a devastating effect on the plants that are used as animal feed and as animal grazing pastures (Godish et al.,, 2015; Gurjar, Molina, & Ojha, 2010; Brady, 1990; Tisdale, Nelson, & Beaton, 1985; Cullison & Lowrey, 1987). Odour is also an important consideration that air quality engineers must consider. In most cases, they are concerned about the permit limits or other quantitative limits at the expense of the smell of the environment. A clear understanding of the welfare effect of air pollution and poor air quality is helpful in the determination of airflow rate and filter velocity for the spray booth design. 

Face velocity allows the movement of adequate air at sufficient speed to trap particulates and solvent emissions while directing them to the filters and out of the exhaust stack. The filter velocity requirements allow slow movement of air through the filters so that they can capture the particles and maintain the required pressure drops in the filters. Various spray booths have differently faces located at the unique places, e.g., open face booth, cross or end the draft, downdraft, semi-downdraft and side downdraft both. 

Calculating face velocity 

According to the TCEQ (2011), the required minimum face velocity is 100 feet every minute. For computation purpose, the flow rate of the exhaust fan, the flow rate of air make-up unit fan both in cubic feet per minute and the area of the booth openings that are usually open when it is operating must be determined. For the case scenario, there is only one unit assuming that the radius of the air 9ntake is 3.0ft, the intake area can be calculated as follows 

Area = πr 2 

=3.14*3.0*3.0 

=28.26 ft 2 

The min flow rate can be obtained by subtracting the min air makeup unit airflow from the minimum exhaust fan flow rate 

= 10,000 ft 3 /min - 5760 ft 3 /min 

= 4240 ft 3 /min 

Divide the obtained figure by the intake area calculated earlier 

=4240/28.26 

= 150.04 ft/min face velocity 

The face velocity is above the minimum requirement of 100 ft/min, and therefore the design is compliant with the state permit requirement. The next step is to calculate the filter velocity for the booth. According to the TCEQ (2011), the maximum filter requirement is 250 feet per minute. The calculation of filter velocity requires the flow rate of the exhaust fan in cubic feet per minute and the area of all the booth filters. In the scenario, there are two openings for the booth. The sum of the two filter areas are therefore obtained 

= 20.0 ft 2 + 20.0 ft 2 = 40 ft 2 

The flow rate is then divided by the filter areas 

= 4240 ft 3 /min/40 ft 2 

=106.0 ft/min filter velocity which is below the maximum velocity of 250 ft/min. The design is still within the regulatory limits for the permit. The booth is appearing to be compliant with the regulatory requirements as currently engineered. Even if there is no full title V permit, it is still on target of attaining a permit by rule. 

VOC Content Minus Water and Exempt Solvents 

It is necessary to monitor air quality using statistically valid air sampling of various matrices. There are different sampling techniques for gas, particles and vapor matrices. There are three elements of monitoring air quality, i.e., sampling, sample analysis and data analysis. Each of the aspects informs the other. Air sampling should be conducted methodically and adequately to generate the highest quality air sample for both chemical and physical analysis in the lab. According to Phalen & Phalen, (2013), there are four types d air samples, i.e., source sample, area sample, population sample and personal. Descriptive and inferential statistical data analysis techniques will inform the engineer of the relationships, correlation and concentration limits that exceed the requirements and are not necessarily observable from the available data. Statistical data analysis in air monitoring activities allows the comparison of derived results against the required regulatory limits. 

According to the TCEQ (2011), different rules apply to various counties. Businesses that are subject to the rules are required to calculate the VOC content of the coating minus water as well as an exempt solvent to determine the compliance level. In the calculation of the single- component coating minus water and exempt solvent the following formula is used 

Pounds of VOC per gallon of coating =

Where Wv is the weight of VOC in Vm gallons of coating 

Vm is the volume of layer which is assumed to be a gallon 

Vw is the volume of water in gallons that is contained in the Vm gallon of coating 

Ves is the volume of exempt solvent, in gallons that are included in Vm gallons of layer 

In the safety data sheet in the scenario, the water content is 1.0lbs per gallon, and the water density is 8.34lbs. Therefore the gallons of water per gallon of coating = 

=1.0lbs/ gallon * 1 gallon of water/8.34lbs of water density 

= 0.12 gallons of water per gallon of coating. 

The exempt solvent n the scenario contain 0.5 lbs/gallon of coating 

The gallons of exempt solvent per gallon of coating 

= 0.5 lbs/gallon * 1 gallon of exempt solvent/ 6.64 lbs of exempt solvent density 

= 0.075 

In the scenario, the coating VOC the Wv = 2.8 lbs VOC. 

=2.8 lbs VOC/ 1 gallon of coating volume – 0.12 gallons water volume – 0.075 gallons of exempt solvent 

= 3.47 lbs of VOC/gallon per day 

The regulatory maximum is 6.0 lbs of VOC/hr 

Since the plant is working for five hours in a day on two cars to interior coat, the facility is still compliant with the state permit requirements 

Air quality engineers are helpful to the management by advising them to make informed decisions on the number of hours that such a facility can be used in a day or in a week if the lbs of VOC per day are not compliant with the state permit requirements. The engineer can, therefore, help the management make an informed decision on the production goals. Collaboration with the management team can ensure that the facility remains under permit limit to avoid the full title V air permit. 

Heater and Oven Combustion Emissions 

There are different models and software that are useful for the determination of air quality. Various models are suited to unique atmospheric and structural considerations. Modeling helps in the calculation of the concentration of a contaminant for a known set of variable. According to Gurjar et al., (2010), data can be approached in the following approaches; artificial neural network, Fuzzy Logic, Ranking or time series. 

In the calculations of emissions of products of combustion from heaters and ovens, it is necessary to determine the source of the power in order to understand whether there are products of combustion that are emitted. The burner rating is used to estimate the emissions of products of combustion. The estimation of emission requires the heating value of the fuel in British thermal units per cubic foot. The number of hours that the oven will be in use per year also needs to be determined. 

In the scenario, the interior cure equipment uses a natural gas-fired heater that matches the requirements of the TCEQ. In the computation, the TCEQ natural gas unit emission factor as tabulated for the firing rate of 0.3 MMB tu/hr (lb10 6 scf) and 100 MMB tu/hr (lb10 6 scf) will be used. The air contaminant analytes generated from the natural gas-fired cure for the application of the air permit will involve the following steps. 

Calculations for the short term emissions generated by the heater 

Lbs air contaminant per hour = X X

The natural gas-fired cure heater has a firing rate of 2.1 MMBtu/hr and the firing liners in the curing process are anticipated to have 2,500 hrs/year. The NO x content is reported as 100 lbs/ MMscf (lbs/million scf). 

NO x per hour = 100 lbs NO x /MMscf X 1 scf/1020 Btu X 2.1MMBtu/hr 

= 0.206 lbs NO x per hour 

The CO is tabulated as 84 lbs/MMscf 

= 84 lbs CO/MMscf X1scf/1020 Btu X 2.1 MMBtu/hr = 0.173 lbs CO/hr 

The PM content is tabulated as 7.6 PM/MMscf. The lbs per hour can be obtained as follows 7.6 PM/MMscf X 1scf/1020 Btu X 2.1 MMBtu/hr = 0.016lbs CO/hr 

VOC content is tabulated as 5.5 lbs/MMscf. The VOC per hour is computed as follows 

= 5.5 lbs VOC/MMscf X 1scf/1020 Btu X 2.1 MMBtu/hr = 0.011lbs VOC/hr 

SO 2 content is tabulated as 0.6 lbs/MMscf the SO 2 /hr is obtained as follows 

= 0.6 lbs SO 2 /MMscf X 1scf/1020 Btu X 2.1 MMBtu/hr = 0.001 lbs SO 2 /hr 

The second set of calculations involves the long term annual emission generated from the heater. The hourly emissions are converted to annual emissions using 2,500 hours per year and then to tons i.e. 2000 lbs/ton to obtain the air contaminants per year in tons. The following formula is applicable 

Lbs air contaminant per hour = X X

NO x per annum = X X = 0.258 

CO per annum = X X = 0.216 

VOC per annum = X X = 0.014 

SO 2 per annum = X X = 0.0013 

Pollution Control Technologies 

Air quality control options fall into particulate phased pollutants or gas phased pollutants. The particulate pollutants are measured as a percentage of the particulate matter is captured in three strategies which are effective in air quality improvement. The three include; cyclonic collection, electrostatic collection and different methods of filtration collection. Settling chambers, impingers and cyclones have the ability to capture large and medium sized particles of pollutants. They can include elutriators used for aerosol particle collection and cyclones that include aerosol centrifuges. Their benefits include low cost, durability, low maintenance and simplicity of operations. The disadvantages include low efficiencies for very small particles, likelihood of erosion of components as a result of the abrasive particles and the need for large spaces for the equipment (Phalen & Phalen, 2013; Godish et al., 2015). 

The filtration processes include traditional systems like medium filters that can capture such none sticky particles and fumes. They make for highly efficient systems require moderate power and produce dry disposable waste. They are low cost but need high bag replacement. They also have a high potential for fire hazards (Phalen & Phalen, 2013; Godish et al., 2015). 

Advanced filtration systems include wet scrubbers and spray chambers. Both capture very small particles and are ideal in different pressures and do not generate dust. It has one disadvantage in that the entire process involves water. The waste water becomes another challenge that must be handled by the facility (Phalen & Phalen, 2013; Godish et al., 2015). 

Gas phased pollutants can be captured through PM-capturing, thermal oxidizing, absorption and biological treatment. The different approaches in each strategy allow the engineer to match the different types of pollutants to the control. Thermal oxidizers are gas combustion chambers with very high temperatures 540 o C -815 o C. They can accommodate a range of gasses and work similarly to a flare regarding combustion that reduces the effluent to less complex gases. Little maintenance is required yet the process is very efficient. There are potentials for carbon dioxide and monoxide as by-products (Phalen & Phalen, 2013; Godish et al., 2015). 

Flare systems are used for hydrocarbon rich gases which are in the range of the just below the upper explosive limit and above the lower explosive threshold. The explosive gasses are combusted at an efficiency rate of about 99%. However, it has one disadvantage in that natural gas is used to flare up the system. The gas also keeps the pilot lit and produces other by-products of combustion (Phalen & Phalen, 2013; Godish et al., 2015). 

Catalytic systems are catalyst filled filters that operate at high-temperature 370 o C – 480 o C to treat gasses at near lower explosive limits. Its benefits include low maintenance requirements, and low system pressures drop an indicator of electrostatic precipitators. It has the advantages of reducing footprint and the use of fuel by other systems. However, its disadvantages range from inefficiencies in the design especially in colder temperatures and high potential of catalytic chamber clogging by particles. The replacement of the catalyst is also expensive (Phalen & Phalen, 2013; Godish et al., 2015). 

Absorption systems are designed in a way that they take advantage of the stickiness of gas molecules using the van der Waals attraction. Can either be solid or liquid systems. The process is accomplished using solid media system where beds are packed with different packing media including metal, glass, plastic beads and activated carbon creating a sorbent environment for molecules that are traveling in the system. The air engineer is informed by the polarity of the particles on which media to use in the system to target the gas molecules that are of interest. The specificity of the technology is one of its benefits in addition to its ability to incorporate high-temperature gases to destroy other gases. Some of the disadvantages include the potential of clogging due to the pressurized gas stream. Flammable media like activated charcoal is compounded by the absorption of combustible organics. Liquid media can be used and recycled but can be expensive given the effectiveness of some of the liquids to capture select molecules, corrode and contaminate (Phalen & Phalen, 2013; Godish et al., 2015). 

Absorption systems can be designed to use solid or liquid. Solid based media scrubbers include packed tower scrubber designs which can accommodate different gas molecules using sodium, carbonate lime including other packed media. Flue gas and others can be dry scrubbed using aerosols which is later semi-dried using a reaction chamber. Liquid phased scrubbers can include water which is mixed with other mineral slurries or even acid (Phalen & Phalen, 2013; Godish et al., 2015). 

Biological treatment systems are appropriate in digesters and not in capturing gasses like organic acids, esters, toxic gases, and Ketones. The bio scrubbers have different design types, and their advantages include their efficiency. The disadvantages include high maintenance requirements, the costs of maintaining the microbes necessary to keep the biofilter and the packing beds charged. Lastly, the microbes are sensitive to temperatures and pressures (Phalen & Phalen, 2013; Godish et al., 2015). 

For the air quality project, a combination of techniques can be useful in pollution control technologies. The management can use the catalytic system for treating the gases near their low explosive limits. Similarly, the booth can be fitted with an absorption system to capture any sticky gas molecules. The absorption system will incorporate a solid system with a combination of metal and activated charcoal or plastic beads and activated charcoal. 

Process Flow Diagram 

R  

CED

Washer

Pre-treatment

Baking Oven

eady for Painting 

Sanding

Sealing

Sound dampers

Drying

Cleaning

Prime surface Application

Baking Oven

Cleaning

Basecoat

Flash off

Clear Coat

Baking Oven

Inspection

Repairs

Waxing

Reference 

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Cullison, A., & Lowrey, R. (1987). Feeds and feeding (4th ed.). Englewood Cliffs, NJ: Prentice Hall 

Godish, T., Davis, W. T., & Fu, J. S. (2015). Air quality (5th ed.). Boca Raton, FL: CRC Press. 

Gurjar, B., Molina, L., & Ojha, C. (2010). Air pollution: Health and environmental impacts. Boca Raton, FL: CRC Press. 

Henneberry, Y., Kraus, T., Krabbenhoft, D., Bachand, P., & Horwath, W. (2011). Removal of inorganic mercury and methylmercury from surface waters following coagulation of dissolved organic matter with metal-based salts. The Science of the Total Environment, 409(3), 631-637. 

Hill, J., & Feigl, D. (1987). Chemistry and life: An introduction to general, organic, and biological life (3rd ed.). New York, NY: Macmillian Publishing. 

MacDougall, A. H., Eby, M., & Weaver, A. J. (2013). If anthropogenic CO2 emissions cease, will atmospheric CO2 concentration continue to increase? Journal of Climate, 26(23), 9563-9576. Retrieved from http://www.researchgate.net/publication/258772723_Would_atmospheric_CO2_concentration_contin ue_to_increase_if_anthropogenic_CO2_emissions_were_to_suddenly_cease 

Phalen, R. F., & Phalen, R. N. (2013). Introduction to air pollution science: A public health perspective. Burlington, MA: Jones & Bartlett Learning. 

Texas Commission on Environmental Quality. (2011). Surface coating facilities: A guide for obtaining air authorization in Texas. Retrieved from https://www.tceq.texas.gov/searchpage?cx=004888944831051571741%3Auk3yh4pey8&cof=FORID%3A11&q=Surface+Coating+Facilities%3A+A+Guide+for+Obtaining+Air+Auth orization+in+Texas 

Tisdale, S., Nelson, W., & Beaton, J. (1990). Soil fertility and fertilizers. New York, NY: Macmillan Publishing. 

Withgott, J., & Brennan, S. (2011). Environment: The science behind the stories (4th ed.). San Francisco, CA: Benjamin Cummings.