Technical Support Document

for

Revised TPQ Method for EHS Solids in Solution

February 2011

Office of Emergency Management

Office of Solid Waste and Emergency Response

U.S. Environmental Protection Agency

Washington, D.C.
2

I. Introduction........................................................................................................................... 3

II. Background ........................................................................................................................... 4

III. Proposed Revised Method for Solids in Solution TPQ...................................................... 5

IV. Experimental Data on Releases of Aerosols ....................................................................... 7

V. Use of Aerosol Release Data to Revise TPQs for EHS Solid in Solutions........................ 8

A. Appropriate Experimental Data 8

B. Consistency Issues for EHS Liquids 9

VI. Alternative Approaches Considered ................................................................................. 10

A. Use Original Ranking Index Method to Develop New TPQs 10

B. Use Old Lower TPQ Divided by Aerosol Airborne Fraction 11

C. Using ARF Limited to Smaller Aerosol Sizes 11

1. Small Size Aerosols Used in Toxicity Tests 12

2. Particle Size and Exposure 12

3. Solvent Evaporation from Aerosols 13

VII. Literature Survey for Liquid Aerosol Release Data........................................................ 13

A. DOE Aerosol Data for Aqueous Solutions 13

1. Thermal Stress from Boiling 14

2. High Pressure Venting Below Liquid Level 14

3. Pressure Venting Above the Liquid Level 15

4. Superheated Liquid 17

5. Burning Organic Fire Burning to Complete Dryness or Burning Solvent over 

Aqueous Phase Burning to Complete Dryness 18

6. Aqueous Solution or Air Dried Salt under Gasoline Fire on Heat Conducting Surface 

(i.e. metal) 19

7. Aerodynamic Entrainment and Re-Suspension 19

B. Data from CCPS Vapor Cloud Modeling “Aerosol Project” 20

VIII. References.................................................................................................................... 22

APPENDIX A: Assigning Threshold Planning Quantities (TPQs) for Extremely Hazardous 

Substances.................................................................................................................................... 26

APPENDIX B: Comparison of Current TPQ (Volatilization) vs Effective TPQ 

(Aerosolization)........................................................................................................................... 28

APPENDIX C: EHS Solids TPQ Comparison......................................................................... 36

APPENDIX D: Estimation of % Mass Aerosol vs. Diameter Size for Aerosol Releases .... 41
3

I. Introduction

Section 302 of the Emergency Planning and Community Right-to-Know Act (EPCRA) required 

EPA to develop a list of acutely toxic chemicals [known as Extremely Hazardous Substances or 

EHSs)] and a threshold planning quantity (TPQ) for each substance. Any facility that has an 

EHS at or above it TPQ must notify local and state emergency planning organizations and must 

participate in the emergency planning process with its Local Emergency Planning Committee

(LEPC). EPA developed TPQs for each chemical based on its acute toxicity, physical state (gas, 

liquid or solid) and potential for airborne dispersion. 

EPA is proposing a rule to consider an alternative approach for the threshold planning quantity 

(TPQ) for chemicals on the Extremely Hazardous Substances (EHSs) list that exist as solids in 

solution form. The current TPQ for solids in solution is based on an assumption that the entire 

quantity of the solid chemical in solution at a facility has the potential to become airborne in the 

event of an accidental release. In 1999, Syngenta Crop Protection, Inc. (formerly Zeneca, Inc, 

formerly ICA Americas) requested EPA to revise the TPQ for the chemical paraquat dichloride, 

a solid chemical which is used commercially in solution, approximately 23-44% by weight

(Zeneca 1999). Syngenta stated that paraquat dichloride in liquid (solution) form does not 

consist of particles suspended in liquid, but completely dissociated ions. Based on a vapor 

pressure measurement study for Paraquat (Mcnab 2001), Paraquat has a vapor pressure of 2.2 x 

10-5 mm Hg at 145.5°C and 5.0 x 10-4 mm Hg at 181.2 °C. Its vapor pressure is not detectable at 

the limit of detection of 7.5 x 10-8. It decomposes before reaching a boiling point with 

decomposition temperature between 320-340°C. The vapor pressure at 320°C and 340°C is 

estimated to be 4.0 mm Hg and 9.6 mm Hg, respectively (Mcnab 2001). Because of the 

chemical‟s very low vapor pressure, EPA believes releases to air via volatilization will be very 

low for paraquat dichloride. However, accidental releases of liquid aerosol droplets of paraquat

dichloride in solution under certain circumstances are possible.

EPA researched data and studies on aerosol air releases of liquids and solutions to investigate 

how much aerosol remains airborne during accidental air releases of liquids. Results of this 

research, explained in more detail in Section VIII, show that much less than 100% of an amount 

of solid in solution involved in an accidental release to air is expected to remain airborne for 

distances beyond a facility‟s fence line. Therefore, EPA believes that the assumption of 100% 

potential airborne release for solids in solution is too conservative and a new approach is 

warranted. 

EPA‟s revised TPQ method for EHS solids in solution and supporting data was peer reviewed 

and this Technical Support Document has been revised based on peer review comments. The 

specific comments from the peer review and response to peer review comments are found in a 

separate document, Peer Review of Technical Support Document for Revised TPQ Method for 

EHS Solids in Solution, which is available in the docket. 

In general, two of the three peer reviewers agreed that the revised TPQ method was logical with 

a sound scientific basis, and that the method was clear and understandable. One reviewer 
4

thought the use of Immediately Dangerous to Health and Life values (IDLH) and animal lethality 

data for determining the Level of Concern (LOC) used in developing TPQs was not appropriate, 

although he did think EPA had appropriately ranked the chemicals by potential hazard to the 

public. EPA agrees that the use of IDLH is an imperfect measure for determining the LOC, EPA 

used safety factors and other human toxicity data where appropriate to also determine the TPQs. 

All reviewers agreed that the method was sufficiently conservative to fulfill the accident 

prevention purposes of section 302 of EPCRA. Some improvement was needed to present the 

information in a better way for the regulated community to understand and apply and the revised 

technical support document addresses those concerns. EPA also added examples for how 

facilities should apply the TPQ for various situations. Based on one reviewer‟s comment, EPA 

strengthened and clarified the reasoning for supporting the option chosen versus the alternative 

options. 

In general, the three reviewers agreed that the revised TPQ method was logical with a sound 

scientific basis, and that the method was clear and understandable. They agreed that the method 

was sufficiently conservative to fulfill the accident prevention purposes of section 302 of 

EPCRA. All three reviewers thought that the revised methodology was fairly consistent with the 

approach used for setting other TPQs. However, one reviewer thought EPA should consider 

lowering the TPQs for some of the EHS liquids. EPA has provided explanations for why this 

should not be done; mainly there are reasons that a higher potential for airborne dispersion 

should be assigned to liquids as compared to a non-volatile solid in solution. The reviewers were 

not able to provide any other approaches or data that should be used to revise the TPQ method 

for solids in solution.

II. Background

The TPQs were originally developed as relative measures of concern rather than absolute values. 

The TPQ is not necessarily applicable to any specific situation with respect to predicting the 

actual quantity or “safe” level. This is best determined by the local planning authorities using 

specific parameters for that facility because there are wide variations of site-specific conditions 

that affect airborne dispersion. 

TPQs were developed using a ranking approach based on each chemical‟s physical state, acute 

toxicity and an air dispersion factor (V), the potential for the chemical to become airborne. See 

Appendix A for a more detailed explanation for the basis of the TPQs. The ranking index was 

defined as the Level of Concern (LOC) divided by V. V was set equal to 1 for gases. For liquid 

EHSs, V is a calculated number based on a volatilization modeling equation and is actually the 

rate of volatilization (mass vaporized per unit time) per mass of liquid spilled for a spill, assumed 

to be 1 cm deep. For liquids, V has the units of (minutes)-1.

Solid chemicals have two TPQs: 10,000 pounds or a lower TPQ if the solid is a) in powder form 

with particle size less than 100 microns, b) molten, c) in solution, or d) has a National Fire and 

Protection Association (NFPA) rating of 2, 3, or 4 for reactivity. The lower TPQ for a solid 
5

chemical is based on an index equal to the LOC divided by V where V is equal to 1, similar to 

gaseous forms of EHS. For solids with particle size of 100 microns and higher, the TPQ is 

10,000 pounds. For chemicals that are molten solids, the amount on-site is multiplied by 0.3 

before comparing to the lower TPQ for reporting purposes because 0.3 is the maximum fraction 

estimated to potentially volatilize. 

Details of the methodology used to derive the TPQs are found in the November 16, 1986 interim 

final rule and April 22, 1987 final rule developing the EHS list (51 FR 41570 and 41593) and 

(52 FR 13378) and in the technical support documents in the rulemaking record (USEPA 1986 

and USEPA 1987a, b, c, d). These documents are found in the docket for this proposed 

rulemaking. 

III. Proposed Revised Method for Solids in Solution TPQ

Solid EHS (except reactive solids) have a 10,000 pound TPQ or a specified lower TPQ 

(based on V=1) for certain forms such as solid in solution. 

Based on review of experimental data on accidental releases of solutions, EPA is proposing that 

the maximum fraction of aerosol release of non-reactive solid in solution that could be expected 

to remain airborne and affect a community outside a facility‟s fence line is 0.2. Facilities would 

multiply the amount of EHS chemical on-site handled as a solid in solution by 0.2 and then 

determine if this amount equals or exceeds the established lower TPQ. If the amount in solution 

on site multiplied by 0.2 does not equal or exceed the threshold, then the facility is not subject to 

the emergency notification requirement for that substance. This has the same effect as raising 

the TPQ by a factor of five (5) for a solid in solution, without listing a third TPQ in the 

regulations for non-reactive solids. This proposed procedure is the same as is done now for 

molten solids, except that molten solids apply a fraction of 0.3 (30%). 

Appendix C contains a list of the 157 EHS solids with their existing lower TPQs and what the 

effective TPQ would be if the proposed revised method is used. The effective TPQ in Appendix 

C is the amount of the solid EHS in solution, below which a facility would not be required to 

report the EHS under Section 302 of EPCRA. The 157 solid chemicals are also listed in 

Appendices A and B of 40 CFR part 355 with two TPQs (the higher TPQ is 10,000 pounds). 

The revised method does apply not to the twelve solid EHS chemicals that are reactive solids

(noted by footnote “a” in Appendix A and B of 40 CFR part 355). These reactive solids are not 

included in Appendix C of this document. Reactive solids are highly reactive with air or water 

or are explosive. Because of this, they are more likely than other solids to be dispersed into air 

due to the energy or heat created when they react. Other reactive solids form toxic gases when 

they react with air or water. The explanation for not assigning a 10,000 pounds TPQ to each of 

the reactive solids is discussed in a document (USEPA 1987c) which can be found in the docket 

to this rulemaking.

The amount of solid to be multiplied by 0.2 should include only the weight of the chemical and 
6

not the solvent or other chemicals in the solution. The amount of solid in solution may be 

determined by multiplying the weight percent of the solid in solution in a particular container by 

the quantity of the solution. Solutions include aqueous or organic solutions, slurries, viscous 

solutions, suspensions, emulsions, and pastes.

For example, a facility has on-site 4,000 pounds of solution of 37% by weight paraquat

dichloride. Therefore, this solution contains 1,480 pounds of paraquat dichloride (0.37 x 4,000 

lbs.). The facility would multiply 1,480 pounds by 0.2, which equals 296 pounds. This amount 

is then compared to the TPQ for paraquat dichloride, which is 10 pounds. Because 296 pounds 

exceeds the 10-pound TPQ, the facility is required to comply with the emergency notification 

requirements of Section 302 of EPCRA.

As another example, a facility has 10 gallons of a solution of 37% by weight paraquat dichloride 

on-site. The density of the solution is 9.33 pounds per gallon. Therefore, this solution contains 

34.5 pounds of paraquat dichloride (10 gal x 9.33 lb/gal x 0.37). The facility would multiply 

34.5 pounds by 0.2, which equals 6.9 pounds. This amount is then compared to the TPQ for 

paraquat dichloride, which is 10 pounds. Because this amount is less than the 10-pound TPQ, 

the facility is not required to comply with the emergency notification requirements of Section 

302 of EPCRA.

Facilities that handle both the powdered and solution forms of a particular solid EHS, will have 

to consider the quantities of each form and the particle size of the powder to determine whether 

they exceed a TPQ. Several examples are given below for a solid chemical with a listed lower 

TPQ of 500 pounds.

Solid in solution exceeds lower TPQ, powder below 10,000 pounds. A facility has 5,000 

pounds of a pure EHS solid powder with particle size greater than 100 microns. They also have 

a 1000 gallon tank of an EHS solid in solution at 35% concentration and density of 9 pounds per 

gallon.. The 5,000 pounds of EHS powder less than 100 microns size does not exceed the 

applicable 10,000 TPQ. However, the amount of solids in solution on-site is 3150 pounds (1000 

gallons x 9 pounds per gallon x 0.35). Multiplying the 3150 pounds of solid in solution by 0.2 

results in 630 pounds, which is greater than the lower TPQ of 500 pounds. The facility must 

report under Section 302 of EPCRA based on exceeding the lower TPQ.

Solid in solution below lower TPQ, powder exceeds 10,000 pounds. A facility has 

11,000 pounds of a pure EHS solid powder with particle size greater than 100 microns. They 

also have a 2,000-gallon tank of an EHS solid in solution at 10% concentration and density of 9 

pounds per gallon. The 5,000 pounds of EHS powder greater than 100 microns size exceeds the 

applicable 10,000 TPQ. The amount of solids in solution on-site is 1,800 pounds (2,000 gallons 

x 9 pounds per gallon x 0.10). Multiplying the 1,800 pounds of solid in solution by 0.2 results in 

360 pounds, which is below the lower TPQ of 500 pounds. The facility must report under 

Section 302 of EPCRA based on exceeding the 10,000 pounds TPQ.
7

Solid in solution below lower TPQ, powder less than 10,000 pounds. A facility has 5,000 

pounds of an pure EHS solid powder with particle size greater than 100 microns. They also have 

a 1,500 gallon tank of an EHS solid in solution at 15% concentration and density of 9 pounds per 

gallon.. The 5,000 pounds of EHS powder greater than 100 microns size does not exceed the 

applicable 10,000 TPQ. The amount of solids in solution on-site is 2,025 pounds (1.500 gallons 

x 9 pounds per gallon x 0.15). Multiplying the 2,025 pounds of solid in solution by 0.2 results in 

405 pounds, which is below the lower TPQ of 500 pounds. The facility is not required to report 

under Section 302 of EPCRA because it does not exceed the lower 500 pounds or the 10,000 

pounds TPQ.

Powdered product less than 100 microns, processed into solution. If the same amounts of 

solid EHS were involved as the same scenarios above, except the powder has a particle size of 

less than 100 microns, then the lower 500 pound TPQ would apply to the powder instead of the 

10,000 pounds. If either the amount of powder or solid in solution would exceed the lower TPQ, 

the facility would be required to report under Section 302 of EPCRA.

IV. Experimental Data on Releases of Aerosols

EPA found a comprehensive study by US Department of Energy (USDOE 1994) that compiled 

experimental data on aerosol releases of heavy metal (uranium) salts in solution. The study 

estimated the fractions of liquid aerosol releases that remained airborne for various release 

scenarios. EPA reviewed and summarized the scenarios with the highest airborne release 

fractions (ARF) in Section VIII of this document. The accidental release scenario with the 

highest airborne release fraction had an ARF of 0.2. The airborne fractions generally contain 

aerosol sizes less than or equal to 100 microns, the size above which droplets are expected to fall 

out before they reach a community outside a facility. 

EPA also looked at experimental data collected by the Center for Chemical Process Safety 

(CCPS) for aerosol releases of water and cyclohexane. CCPS, a directorate of the American 

Institute of Chemical Engineers (AICHE), was established in 1985 to develop and disseminate 

technical information for use in the prevention of major chemical process incidents. CCPS 

develops and publishes guidelines, conducts seminars, symposia, training programs and meetings 

on chemical process-safety matters; and cooperates with other organizations, both internationally 

and domestically, to promote process safety. CCPS‟s activities are supported by funding and 

expertise from over 100 entities including, industry, consulting firms, and governmental 

organizations. USEPA is a member of this organization. 

In 1989, the CCPS Vapor Cloud Modeling Subcommittee began an “Aerosol Project” to meet 

some of the research objectives proposed to the US National Vapor Cloud Research Committee, 

which included developing a superheated liquid release model and developing experimental .data 

to validate the model. The experimental field data was the result of field controlled-release 

experimentation by CCPS with financial assistance by special grants from some of the CCPS 

sponsors and from the USEPA and USDOE. The experimental superheated liquid release data 

was developed, documented, peer reviewed and, where necessary, corrected. The Vapor Cloud 
8

Modeling Subcommittee contracted a review of the fundamental basis for the RELEASE model, 

and to make model improvements to reconcile the cyclohexane, chlorine, and methylamine test 

data. The results of the model development and the experimental field data used were published 

in a CCPS concept book (Woodward and Johnson, 1999). 

EPA did not use the aerosol release fraction from the CCPS data because these liquids did not 

contain any solid material in solution. Specifically, the reported airborne release fraction for 

water varied from 0.03 to 0.54 and for cyclohexane varied from 0.36 to 0.94. These data are

discussed in further detail in Section VIII of this document. Cyclohexane with a vapor pressure 

of 95 mm Hg is more volatile than water with its vapor pressure of 24 mm Hg. It is not a good 

comparison to use aerosol release fractions of volatile liquids to estimate the aerosol release 

fractions of a solid in solution because solids are not very volatile. The water aerosol data might 

be a close surrogate for estimating a release of an aqueous solution of the solid, but it does not 

have the important constituent of a dissolved solid, which might influence the amount of aerosol 

remaining entrained in the air. However, the CCPS data for water supports EPA‟s belief that 

assuming a 100% airborne liquid aerosol release is inappropriate (too high) because the water 

aerosol fractions measured in the experiments were less than one (less than 100%). 

CCPS also had experimental release data for CFC-11 and chlorine (both gases), and 

methylamine (a highly volatile chemical with a vapor pressure of 300 mg Hg), but EPA did not 

consider this data for use as a good analogy because of their high volatility and they did not 

contain any solids.

V. Use of Aerosol Release Data to Revise TPQs for EHS Solid in Solutions. 

A. Appropriate Experimental Data 

The original TPQ rationale for solid in solution TPQ was based on using conservative worst-case 

scenarios and assuming 100% of the solution would be released as aerosol. Both the DOE and 

CCPS data support the argument that assuming that 100% of the liquid aerosol release remains 

airborne is too conservative. 

The USDOE data (USDOE 1994) have results from several release scenarios with the maximum 

airborne release fraction of 0.2. The value is based on the scenarios of aqueous solution or airdried salts under gasoline fire on a metal surface. (See summary table below). 

DOE Aerosol Release Scenarios with Highest ARF

Aerosol Release Scenario Maximum Airborne Release Fraction (ARF)

Thermal Stress from Boiling 0.002

High Pressure Venting Below Liquid Level 0.12

Pressure Venting Above the Liquid Level 0.002

Superheated Liquid 

 Temp. ≥50 oC and ≤ 100 oC

0.1

Superheated Liquid Temp ≤50 oC 0.01
9

Burning Organic Layer Over Aqueous Solution 0.1

Aqueous Solution or Dry Salt under Gasoline 

Fire on Metal

0.2

Aerodynamic Entrainment and Re-Suspension 0.1

Using the highest airborne release fraction rather than an average result of the scenarios would 

be more consistent with the intent of the emergency planning program to plan for the worst-case 

scenario. This data is a good surrogate to use to predict maximum potential aerosol release 

fraction of EHS solids in solution in event of an accidental release. Water is probably the most 

common solvent that would be used with most of the EHS solids, whether they are dissolved, 

suspended,or emulsified in water. Many of the EHS solids are pesticides and pesticides are 

commonly applied as water solutions or emulsions. 

Most of the DOE experimental aerosol release data had aerosol sizes of less than 100 microns. 

The water and cyclohexane aerosol release data compiled by CCPS had much larger mean 

aerosol diameter sizes, generally over 100 microns. Because it is likely that aerosol releases with 

diameters larger than100 microns will fall out of the air before they reach a community, the 

water and cylcohexane aerosol experimental data are not that useful for our purposes of 

determining TPQs for solids in solution.

In the EHS final rule of April 22, 1987, EPA had modified the TPQs for solid chemicals so that 

only powdered solids with particle size less than 100 microns would be subject to the lower 

TPQ. Otherwise, the TPQ defaults to 10,000 pounds. This decision was based on data 

indicating that a particle of a size less than 100 microns are not likely to be deposited more than 

100 meters from the source (USEPA 1995) . For example, for a typical wind speed of 10 mph, 

particles larger than about 100 microns are like to settle out within 6 to 9 meters from the point 

of emission. Particles that are 30 to 100 micron in diameter are like to undergo impeded settling 

and are likely to settle with a few hundred feet. The 100-micron cutoff is also consistent with 

CERCLA regulations (for reportable quantities) which also uses a 100-micron particle size level 

for powdered materials (40 CFR 302.4). For purposes of establishing threshold planning 

quantities, EPA chose a distance of 100 meters (330 feet) to represent the distance from a source 

inside a chemical facility to the point where the community might be exposed (USEPA 1987a)

B. Consistency Issues for EHS Liquids

EHS liquids could also be released accidentally as aerosols via the same catastrophic scenarios 

(overpressure, superheating) as liquids. It could be argued that perhaps the TPQ method for 

solids in solution could apply to liquids. However, this goes against the intuitive ranking of the 

extent and likelihood of airborne release by physical state as being higher for gases, lesser for 

liquids and even less for solids in solution. Currently the release scenario used for developing 

the liquid TPQs requires only a spill of the liquid, a loss of containment. The liquid then escapes 

into the air by volatilization. An airborne release of solids in solution will require more than a 

failure of containment and will requires an energy source such as overpressure or high 
10

temperature to drive the solution into the air and create aerosol droplets. Not all of the droplets 

will stay airborne (unlike volatilized vapors), and affect the community, whose exposure depends 

on droplet size and distance to the facility fence line. 

Thus, to address any consistency issues, EPA also wanted to determine if the current TPQ 

method for liquids gave more conservative (or at least as conservative) TPQs (lower thresholds) 

when compared to using the TPQ method as proposed for solids in solution. To make this 

comparison, a new TPQ, based on V=1, was calculated for each liquid chemical. Then this TPQ 

was divided by (0.2) to determine the amount of liquid on-site below which a facility would not 

be subject to reporting requirements. This amount is called the effective TPQ for purposes of 

this analysis. For 116 out of the 163 EHS liquids, current TPQs based on volatilization were still 

smaller than or equal to the new effective TPQs based on aerosolization. Most of the other 47 

liquids had current TPQs that were twice the effective TPQ. The results of this analysis are in a 

spreadsheet in Appendix B.

Further examination of the 47 liquid chemicals was undertaken to see why these had current 

TPQs greater than the effective TPQs. For most EHS liquids, V=1 is about ten times greater 

than the actual V. Given that the same LOC values are being used to calculate new indexes 

when V=1, one might expect the new TPQV=1 to differ from the current TPQ by about a factor of 

ten (Index = LOC/V) for a given chemical. However, because of the manner in which a TPQ 

was assigned to an index range, the difference between most TPQV=1 and the current TPQ is a 

factor of 2 or 5. When you divide a TPQV=1 by 0.2, the result is some effective TPQs with values 

of 5, 50 and 5000. However, there are no current assigned TPQs of 5, 50 or 5000 pounds. 

Actual TPQ values are 1, 10, 100, 500, 1,000 and 10,000 pounds. Therefore, where the effective 

TPQs of the 47 liquids are either 5, 50 or 5,000 pounds, the comparison of current TPQ versus

effective TPQ may not be valid. 

EPA believes that using the volatilization model to establish V for liquid TPQs is still 

appropriate. The spilled liquid at boiling point scenario is probably the most prevalent worstcase scenario that is reasonable to use for establishing TPQs for liquids. 

VI. Alternative Approaches Considered

A. Use Original Ranking Index Method to Develop New TPQs

TPQs were developed using a ranking approach based on each chemical‟s physical state, acute 

toxicity and V, the potential for the chemical to become airborne. The ranking index was 

defined as the Level of Concern (LOC) divided by V. V was set equal to 1 for gases and solids 

in powder form with particle size less than 100 microns. For solids with particle size of 100 

microns and higher, the TPQ is 10,000 pounds. For chemicals that are molten solids, the amount 

on-site is multiplied by 0.3 to before comparing to the lower TPQ for reporting purposes,

because 0.3 is the maximum fraction estimated to potentially volatilize.

For liquid EHS, V (the potential to become airborne) depends upon the property of volatility 
11

(evaporation of liquid into gas phase). The same calculation for V for liquids cannot be used for 

solids, which are basically non-volatile materials at ambient temperatures. 

Most of the values for V for the liquids are approximately 0.1 (See Appendix B). Using a higher 

V equal to 0.2 for solids in solution implies that in the event of an accidental release, more of the 

solution will become airborne than if it were volatilized from a liquid spill. Because there are 

different mechanisms involved in the two types of releases, it may not be comparable to use the 

0.2 as a substitute for V for solids in solution. 

In addition, if EPA were to use the airborne release fraction of 0.2 as a substitute for V when 

calculating the index ranking, this would be inconsistent with the TPQ method used for molten 

solids. For molten solids, the maximum fraction expected to become airborne by volatilization 

was not used to calculate the index. Index calculations for molten solids were based on V 

equaling 1 and then applying the volatilized fraction quantity of the molten solid on-site to be 

compared with the lower TPQ.

B. Use Old Lower TPQ Divided by Aerosol Airborne Fraction

Another alternative was to apply the ARF to the existing lower TPQ for solid to develop a new 

TPQ. For example, the lower TPQ for paraquat dichloride is 10 pounds. Dividing the 10 pounds 

by 0.2, the maximum expected aerosol release fraction for a solution, would result in an 

additional TPQ of 50 pounds for paraquat dichloride in solution form. Developing and listing a 

third set of TPQs for solids in solution could be potentially confusing to the regulated 

community. For each solid chemical, there already exists two TPQs, one developed based on the 

ranking index methodology of (Index = Level of Concern/V ) and on the default TPQ of 10,000 

pounds for all non-reactive solids not meeting criteria for using the lower TPQ. Using existing 

TPQs of 1, 10, 100, 500, and 1000 pounds each divided by a factor of 0.2 produces another set of 

TPQ values of 5, 50, 500, 2500 and 5000 pounds, respectively.

C. Using ARF Limited to Smaller Aerosol Sizes 

Another approach considered is similar to the proposed approach of multiplying the maximum 

ARF by the amount on-site, except that the ARF would only represent the fraction of the 

aerosols with particles less than respirable size. Through discussions with the petitioner and 

EPA„s November 2003 response to the petition, EPA has considered whether aerosol size should 

be used as a factor in developing new TPQs for solids in solution. Syngenta believed that EPA 

should only consider the dispersion of aerosols with particle sizes less than or equal to 4 microns,

because (1) these smaller aerosols are the size that can enter the lung, (2) the inhalation toxicity 

tests used for the basis of the EHS listing only used very small (2.5 microns) particles (Syngenta 

2001) and (3) EPA defines considers particles under 4 microns to be respirable. Although the 

small size particles were created under laboratory conditions for toxicity testing, Syngenta infers 

that airborne exposure to small particles of paraquat dichloride from an accidental release is not 

possible (Zeneca Ag Products Inc vs. Whitman and USEPA, 2000).
12

A consultant for Syngenta recalculated some of the USDOE airborne aerosol fractions using the 

raw experimental data (median ARF values instead of bounding ARF values) to include only 

aerosols sizes ≤ 4 micron diameter for some accident scenarios (Reiss 2002), which resulted in 

smaller airborne fractions. This approach would require sufficient data on the aerosol size 

distribution for each release scenario to develop a new ARF that would include only aerosols of 

size 4 microns and lower. The ARFs currently cited for the scenarios used for the preferred 

approach include aerosol sizes of 100 microns and lower. 

The USDOE aerosol release data were developed to estimate airborne fractions of liquid aerosol 

releases that were below respirable size as defined by USDOE. By USDOE‟s definition,

respirable size particles are those that can be transported through the air and inhaled into the 

human respiratory system, and are commonly assumed to include particles 10 micron

Aerodynamic Equivalent Diameter (AED) or less. 

1. Small Size Aerosols Used in Toxicity Tests

Aerosols may be defined as a suspension of solid or liquid particles in air. Inhalation acute 

toxicity tests are purposely designed with very small diameter particles in order to ensure that 

particles are small enough to enter rodent lungs and test the toxicity in the lungs. Larger 

particles may not enter deep areas of the lungs and thus test results may be misinterpreted if little 

inhalation toxicity is shown. EPA is not attempting to use the airborne aerosol fraction for 

purposes of risk assessment, but only as a tool to set screening levels for the amounts of 

chemicals on-site ,which may potentially cause harm if accidentally released. One cannot

assume that the size aerosols used in an animal laboratory test would be the same size as those in 

aerosols to which people may be exposed during an accidental release of a solution of solid 

chemical.

2. Particle Size and Exposure

According to EPA, inhalable particles enter the respiratory tract, including the head airways and 

are generally ≤ 100 microns. Thoracic particles (≤ 10 microns) travel past the larynx and reach 

the lung airways and the gas-exchange regions of the lung. Respirable particles (≤ 4 microns) 

are a subset of thoracic particles that are more like to reach the gas-exchange region of the lung 

(USEPA 2004). DOE uses a different size cut of 10 microns, which they consider to represent a 

conservative estimate for respirable size compared to other organizations‟ definitions (USDOE 

1994, I:1.4-5). 

Most particles deposited in upper airways are trapped in mucous that moves to the throat and is

swallowed in a few hours. Thus instead of inhalation exposure deep in the lungs, exposure to 

larger particles of chemicals may occur through dermal exposure to mucous membranes or 

ingestion exposure through swallowing. Emergency planning for EHS chemicals is not limited 

to inhalation exposure only although many of the EHS chemicals listings are based on inhalation 

toxicity. Although airborne exposure is the mostly likely route of exposure, it is not the only 

route of exposure. EPA is concerned about all routes of exposure (inhalation, dermal and 
13

ingestion) to the community. Thus, exposure to larger size aerosols (e.g. those above 4 or 10 

microns) by any route should not be ignored when setting TPQs. 

3. Solvent Evaporation from Aerosols

Even after liquid aerosol droplets are released, some of the solvent may evaporate in air. This 

would result in even smaller size of aerosols or solid EHS particulates in the air to which a 

community would be exposed. One concern is that droplets of size greater than 100 micron 

could settle quickly, dry into a smaller particle sizes and then become airborne again (resuspension). In event of an accidental release, the responsible party should cleanup chemicals 

deposited on facility grounds before additional exposure to the community would take place. 

Data from the USDOE Handbook for re-suspension of liquids and powders from soils and other 

surfaces can be used to estimate the fraction of material re-suspended to be from 4E-3 to 1E-2

(See Section IV. 7 Aerodynamic Entrainment and Re-Suspension).

If the worst-case airborne fraction that leaves the facility‟s site is assumed to be 2E-1 (0.2), then 

the fraction of the release that would fall out and be deposited on the facility‟s site would be 8E1. Assuming that a worst-case fraction 1E-2 (whether as dried solids or liquid droplets) of this 

deposit could be re-suspended, the additional fraction of the original release to become airborne 

would be 8E-3 (8E-1 times 1E-2). Adding the re-suspended fraction of 8E-3 to the original 

airborne release fraction of 2E-1 would yield a total fraction of 0.208. This does not much add 

much to the original amount and rounding appropriately to one significant digit would still result 

in an overall ARF of 2E-1.

VII. Literature Survey for Liquid Aerosol Release Data 

A. DOE Aerosol Data for Aqueous Solutions

The source for this data is the USDOE Handbook, Airborne Release Fractions/Rates and 

Respirable Fractions for Nonreactor Nuclear Facilities, December 1994 Vol. I and II. DOE 

evaluated experimental data and models for many different accident scenarios to determine the 

Airborne Release Fraction (ARF) and Respirable Fraction (RF) for various metal salt solutions. 

DOE used a 10 μm Aerodynamic Equivalent Diameter (AED) to define respirable size. Note

that EPA has a different definition for respirable size (< 4 micron) (USEPA 2004). In some 

scenarios, DOE estimates an Airborne Release Rate (ARR), which is the fraction of the released 

material that has been deposited and then is re-suspended over time.

The ARF values for the scenarios varied widely in order of magnitude, from 1E-1 to 1E-8. 

Because EPA is more concerned with those accidents with higher airborne release and to 

simplify the process of developing TPQs for aerosol type releases, only those DOE scenarios 

with of an estimated ARF 1E-4 or greater were considered for discussion below. Data below are 

reported using the same exponential notation as in USDOE 1994 to better correlate with the 
14

source document.

1. Thermal Stress from Boiling

Bounding ARF = 2E-3 (0.002) 

Data was obtained from experiments involving boiling (bubbles continuously breading the 

surface of the bulk liquid with >30% of the volume of liquid as bubbles) of aqueous solutions in 

flowing air. Mishima, Schwendiman and Radasch (as cited in USDOE 1994, I: 3.13) measured 

ARFs during the boiling of a dilute solution of plutonium nitrate. 100 milliliters of solution was 

placed in a 180 borosilicate beaker on a hot plate. Air and particulate material escaping from the 

beaker was drawn through a glass bell jar and an in-line glass fiber filter. The velocity through 

the filter was estimated to be 3 cm/s. The hot plate temperature varied from 200-220 o C. The 

periods of time for heating varied from 42 to 66 minutes. The ARFs for the four runs at boiling 

ranged from 4.5E-7 to 1.8E-3. Three of the four values ranged from 3E-4 to 1.8E-3. The two 

highest values were estimated from the sum of the filter acid leach and from acid washes of the 

equipment downstream of the filter position due to loss of filter (filter ruptured). These values 

included solution splattered on the vessel onto the glassware. Based on the experiments, a 

bounding ARF value for boiling of aqueous solutions of 2E-3 was selected by USDOE (USDOE 

1994,I:3.1). Twelve other studies were evaluated by Borkowski, Bunz and Schoeck (USDOE 

1994 I:3.15) that examined the airborne release of bubble-burst at the surface of aqueous 

solutions. The ARFs of 2E-3 measured by Mishima, Schwendiman and Radasch bound the 

values measured by the other reported studies by approximately an order of magnitude. 

Particle size was not measured by Mishima, Schwendiamn and Radasch (1968). In one of other 

studies evaluated, Garner et al. (USDOE 1994, I:3.15) measured drop size distribution and total 

entrainment during evaporation in vessels of various diameters (4-in and 12-in. diameters tubes). 

Although ~95% of the drops were in the <20 μm diameter range, the total mass entrained was 

primarily due to drops > 100 μm diameter. Based on this information, EPA will assume that for 

this type of scenario, probably 100% of the airborne particles will have diameters less than 100 

microns. Entrainment values were in the 1E-5 range. 

Bubbling experiments conducted by Heger et al. (USDOE 1994, I:3.15) created airborne drops 

that were bimodally distributed with maxima at 0.3 and 0.8 μm diameter. Entrainment values 

ranged from 1E-7 to 1E-4. Adding tributyl phosphate reduced the surface tension and increased 

entrainment by a factor of 5 to 10. This also increased the generation of larger diameter drops. 

The data indicate that low surface tension solutions can increase the weight percent of airborne 

particles, however, the magnitude of the release is limited due to the increase in drop diameter. 

2. High Pressure Venting Below Liquid Level 

Bounding ARF 0.12

Releases from venting pressurized liquids can range from pinhole leaks in pipes (generating a 
15

mist), to drips from very slow leaks to large jets of liquids that may gush from large holes. The 

amount and aerodynamic size distribution of the spray generated are a function of the size and 

characteristics of the breach, the upstream pressure, and the liquid characteristics (e.g. viscosity, 

density, volatility). 

For purposes of airborne suspension, a conservative assumption would be the pressurized release 

of the liquid via a very fine hole as occurs in a commercial spray nozzle. The size distribution of 

aerosol releases from some commercial spray nozzles as a function of orifice diameter (0.063” to 

0.128”) and upstream pressure (50-200 psig) were shown by Mishima, Schwendiman and Ayer 

(USDOE 1994, I:3.20). The size distribution of the liquid drops decreases with orifice diameter 

and increasing upstream pressure. Figure 3-4 (USDOE 1994, I:3.21) shows cumulative mass 

fraction vs. droplet diameters range from 1E-4 to 8E-1 (0.0001 to 0.80). The droplet diameters 

range from 7 to 500 μm. 

It is not anticipated that drops formed from breaches, cracks, leaks would generate finer drop 

size distributions than equipment specifically designed for that purpose. Therefore, values from 

the 0.063” orifice diameter run at 50 psig were used by USDOE to assume a bounding ARF 

value of 1E-4 for aerosol sizes ≤ 10 μm. While USDOE was focused on finding ARF values for 

only respirable fractions, EPA should be looking beyond that. Figure 3-4 (USDOE 1994, I:3.21) 

shows that at aerosol size ≤100 μm, the cumulative mass fraction varies from 3E-2 to 1.2E-1 

(0.03 to 0.12) depending on the experiment run. Therefore, a bounding value of 1.2E-1 (0.12) is 

expected for aerosol diameter sizes ≤100 μm. Note that although the x-axis of Figure 3-4 is 

labeled as cumulative mass fraction, it appears the data in the table is actually cumulative mass 

percent. Therefore, values cited from the Figure 3-4 have been divided by 100 to obtain the 

mass fraction.

Data for Aerosol Releases from Pressure Venting Below the Liquid Level (50-200 psig)

Cumulative 

mass fraction 

airborne 

For aerosol 

diameter, 

μm

0.003 - 0.0001 ≤ 10 μm

0.03 - 0.12 ≤100 μm

3. Pressure Venting Above the Liquid Level

Bounding ARF 2E-3 (0.002)

Sudden depressurization of a liquid allows the release of dissolved/trapped gases. This sudden 

release of gases may result in bubble formation that can create very small drops upon collapse. 

The drops formed can be carried with the venting gas. Experiments were performed to measure 
16

the ARF due to venting pressurized volumes of aqueous solutions (uranine and UNH) in quasiequilibrium with their pressurizing gases (Sutter, August 1983 as cited in (USDOE 1994, I:3.22). 

100 cm3and 350 cm3of uranine (sodium fluorescein) and UNH (uranyl nitrate hexahydrate) 

solution were released at three pressures of 50, 250 and 500 psig. The solution densities were 

0.99 g/cm3for uranine and 1.54 g/cm3for UNH. An 800 cm3volume container fitted with 

rupture discs, which rupture at a specified pressure, was used for the experiments. Pressurized 

air was introduced into the bottom of the chamber at a pre-selected experimental level, using a 

tube that exits above the liquid level in the containers. At the top of the container, two rupture 

discs were used to create an intermediate chamber between the discs. This chamber was also 

pressurized and a solenoid valve was opened letting the intermediate chamber depressurize. The 

pressure difference across the lower disc becomes too great and disc ruptured causing the upper 

disc to rupture microseconds later. During depressurization, liquid was ejected, samplers 

immediately turned on and aerosol laden air was pulled onto filters. The release was made into a 

cylindrical enclosure, approximately 3 meters high and 2.9 m in diameter with 20 m3volume, 

about the size of a small room. The enclosure had four high volume samplers at 1 m and 1 level 

and one high volume cascade impactor at the 1.5 m level, equipped with appropriate glass fiber 

filters, as they were used to sample aerosol. The experimental device had also been designed for

powder release experiments.

The force acting on the liquid was rapid depressurization leading to vaporization and entrainment 

of the solution. The mass airborne was calculated as the difference between the source mass and 

the mass remaining in the apparatus. The mass airborne increased as a function of pressure for 

the uranine solutions and UNH, but the source volume did not appear significant in determining 

the magnitude of the release. Releases were also lower than anticipated. Particle size 

distributions were measured by cascade impactor samples. Significant evaporation of droplets 

captured in the impactor could mean that the measured size distribution does not correspond to 

that of the actual airborne aerosol. Releases of uranine solutions generated the finest, most 

uniform particles. Table A-6 and A-7 in (USDOE 1994, II:A.6-7) show the median droplet size 

values with their standard deviation for the experimental runs. Median diameters for uranine 

solutions were 4 μm and less, with standard deviation (σg) values of 1.6 to 4. These particles 

were predominantly (70-90%), in the respirable size range of 10 μm or less. The UNH releases 

produced larger particle sizes and more polydispersed aerosols. Diameters ranged from 3 to 45 

μm with σg values from 2.5 to 7.5. Fewer particles of diameter 10 μm or less were generated, 

forming 34 to 76% of the aerosol.

For pressures less than 50 psig (0.345 MPag), the aerosol release fraction ARF varies from 3E-6 

to 5E-5 (USDOE 1994, I:3.22). Between 51 psig (0.352 MPag) and 500 psig (3.45 MPag), the 

ARF vary from a bounding value of 2E-3 for lower density liquids such as uranine to 1E-3 for 

high density liquids (such as UNH) (USDOE 1994, I:3.22) . Tables A-6 and A-7 also show the 

percentage aerosols that were of respirable size (< 10 μm). A consultant for Syngenta (Reiss 

2002) used the data in the Tables A-6 and A-7 with statistical analysis to figure out the fraction 

of droplets that were less than 4 μm diameter for the uranine solution. This statistical analysis 

involved using the median aerosol diameter and standard deviation to calculate the aerosol 
17

diameter at one standard deviation below and above the median diameter and creating a graph 

with those three points on log-log paper showing aerosol diameter versus cumulative mass 

fraction. Using the same statistical analysis and data from Tables A-6 and A-7, EPA determined 

the cumulative mass fraction of aerosols that are below 100 μm. The data results and method 

used are shown in more detail in Appendix D. The table below summarizes data for the aerosol 

releases from only the higher pressures of 250 and 500 psig, because these pressures produced 

significantly higher ARF than that for 50 psig. 

Data for Aerosol Releases from High Pressure Venting Above Liquid Level 

(250-500 psig only)

Solution Maximum 

mass fraction 

airborne 

Median 

aerosol 

diameter, μm

Mass 

fraction

≤ 4 μm

Mass fraction 

of ARF that is 

≤ 10 μm

Mass fraction 

of ARF that is

≤ 100 μm

uranine 0.002 ~ 4 0.47 - 0.64 0.7 - 0.98 1.0

UNH 0.001 11 - 45 0.24 - 0.46 0.68 - 0.99

4. Superheated Liquid

Bounding ARF 0.01 for Temp. ≤50 oC 

Bounding ARF 0.1 for Temp. ≥50 oC and ≤ 100 oC

Liquids heated above the boiling temperature of the liquid/solvent/diluent “flash” upon release; 

that is, the excess heat above the boiling point of the liquid is expended in the bulk vaporization 

of the liquid and the remaining liquid is fragmented into fine droplets. Experiments were 

performed by Ballinger, Sutter and Hodgson to measure the airborne release and size distribution 

of aqueous uranine solution (concentration 10 μg/L) over a limited range of conditions (USDOE 

1994, I:3.28-29). Aqueous solutions were heated to pressures of 57 psig at ~134 o C, 124 psig at 

~161 oC, and 240 psig at 202 oC using source volumes of 700 cm3, 350 cm3and 100 cm3. The 

container was heated using a heat tape on the outside. The liquid was released from the open top 

of the ~4 inch diameter apparatus via a double rupture disk arrangement. The aerosols were 

contained in a stainless steel vessel approximately 3 m high and 2.9 m in diameter with a 20 m3

volume. Once the chamber was depressurized and the liquid ejected, high-volume samplers with 

glass fiber filters were used for mass sampling; a cascade impactor was used for size distribution 

samples. The fraction airborne increased with initial pressure and decreasing source size. In the 

experiments, some of the solution impacted on the ceiling and spread to the walls. Only one run 

(57 psig) had uranine left in the container after release. The residual heat in the device following 

the release my have evaporated the remaining uranine solution from most of the runs; however, 

visual observation of the interior of the chamber following sampling did not show a large amount 

of residue, which would be expected if the significant evaporation took place. 
18

The ARF and RF depend upon the amount of heat available and the heat needed to vaporize the 

solvent. For relatively low energy liquids with temperatures greater than the boiling point but 

less than 50 oC superheat, USDOE assumes bounding ARF and RF values to be 1E-2 and 0.6 

based on the 57 psig run (USDOE 1994, I:3.4). DOE used bounding values of ARF and RF of 

1E-1 and 0.7 (USDOE 1994, I:3.4) based on data from the 124 psig and 240 psig runs for 

scenarios where superheated solutions are between 50 oC and 100 oC of superheat. Median 

diameter and standard deviation from each experimental run presented in Table A.9 (USDOE 

1994, II:A.9) were used to statistically graph aerosol diameter versus cumulative mass fraction. 

The data results and method used is shown in more detail in Appendix D. From these graphs, 

data on mass fraction of aerosols and aerosol sizes are summarized in the table below.

Data for Aerosol Releases from Superheated liquid (Uranine solution) 

Superheat Maximum 

mass fraction 

airborne 

Median 

aerosol 

diameter, μm

Mass 

fraction

≤ 4 μm

Mass fraction 

≤ 10 μm

Mass 

fraction 

≤ 100 μm

≤50 oC 0.01 8.4 0.32 0.62 0.93

≥50 oC and 

≤ 100 oC

0.1 5.9 - 7.7 0.25 - 0.34 0.66 - 0.78 1.0

1

5. Burning Organic Fire Burning to Complete Dryness or Burning Solvent over 

Aqueous Phase Burning to Complete Dryness 

Bounding ARF 1E-1 (0.1)

Scenarios 5 and 6 address potential releases of solid contaminant due to thermal stress for 

organic solutions or organic and aqueous solutions present together. An organic burning liquid 

layer over an aqueous solution produces turbulence. During burning and subsequent 

evaporation, drops of liquid become entrained and suspended into the air. 

Experiments were conducted by Halverson, Ballinger and Dennis using various solutions of TBP 

(tri-normal butyl phosphate) in kerosine with an aqueous solution of an acid (USDOE 1994, 

I:3.44). Either or both solutions contained radionuclides. Small volumes of liquids were place in 

metal beakers and the liquids heated by heating tapes wrapped around the metal beaker. The 

organic liquid ignited and air was drawn up the chimney. Airborne particles were collected on 

glass filters as a function of time. 

Based on several experiments, the conservative upper bound ARF was 1E-1 (rounded up from 
19

7E-2 for highest value in Table 3-13) (USDOE 1994, I:3.6,45). EPA assumed the RF to be 1.0 

in absence of measured value. In absence of additional information, we will assume that 

probably 100% of the particles were less than 100 μm in diameter. The RF was measured for 

only one experiment with a value of 0.99 

6. Aqueous Solution or Air Dried Salt under Gasoline Fire on Heat Conducting Surface 

(i.e. metal)

Bounding ARF 2E-1 (0.2)

Experiments were conducted by Mishima and Schwendiman in a wind tunnel using UNH (uranyl 

nitrate hexahydrate) and air-dried UNH on various substrates (soil, vegetation on soil, asphalt 

and stainless steel) during a shallow pool gasoline fire (USDOE 1994, I:3.43). Liquid UNH was 

placed in a 22-inch diameter flange in the floor of the wind tunnel. One gallon of gasoline was 

poured over the surface, ignited and the air drawn over the burning surface. Airborne particles 

were then sampled. The highest ARF measured was 1.14E-1 for the stainless steel substrate at a 

wind speed of 10 m/s (22 mph). The RF for the stainless steel substrate experiment was 0.34 but 

was as high as 0.75 for other experiments in this scenario including the other substrates (USDOE 

1994, I:3.48). DOE represented the bounding ARF as 2E-1 for this scenario with an RF of 0.3 

when summarizing the data (USDOE 1994, I:3.6), although the highest experimental value 

reported was 1.14E-1. DOE notes that if a substrate conducts heat well, the liquid can be boiled 

rapidly generating conditions much more favorable to generation of airborne liquid droplets. To 

be conservative for the extremely limited data set, DOE probably rounded up the ARF to 2E-1. 

For EPA‟s purposes, we will assume that probably 100% of the particles had diameters less than 

100 microns.

7. Aerodynamic Entrainment and Re-Suspension 

Bounding ARR 9E-5 (0.00009)/hr

a. Liquid Re-Suspension

For those large aerosol droplets that fall out on the facility site without reaching the community, 

the possibility exists that this material could become entrained back into the air by contact with 

wind upon the surface where it was deposited. The DOE Handbook provides re-suspension rates 

know as airborne release rates (ARR) for re-suspension of liquids from soil with unit of measure 

of hours -1. The ARR represents the fraction of deposited material re-suspended over time and 

are in the form of droplets aerodynamically entrained from various surfaces under different 

conditions. 

For example, aerodynamic entrainment (re-suspension) at higher air velocities of UNH solution 

from various surfaces was measured in wind tunnel experiments by Mishima and Schwendiman

(USDOE 1994, I;3.5,41) . From this data, a bounding ARR of 9.0E-5 with an RF of 1.0 is 

conservatively assumed. 
20

DOE notes that there appear to be very large differences in suspension rates under experimental 

test conditions as well as an order of magnitude uncertainty in measurements for individual 

conditions and on this basis, have applied conservative values. Short time frames of less than 

100 hours should be used with these values because they are intended for immediate postaccident conditions and freshly deposited material (USDOE 1994, I:3.5). If one assumed that 

cleanup did not occur for about 4 days (100 hours), the fraction of the deposited release that 

would become airborne would be 9E-3 (9E-5/hr times 100). We can round this up to 1E-2.

b. Powder Re-Suspension

However, large droplets that fall out on the facility site could dry out into smaller particles and 

then become re-suspended. The USDOE Handbook, based on review of literature data, found 

that a bounding re-suspension rate of 4E-5/hr determined by Sehmel and Lloyd was reasonable 

bounding ARR value for re-suspension of powders deposited on various outdoor substrates

(USDOE 1994, I:4.96, 100-101). The ambient conditions would be normal process facility 

ventilation flow or less, or nominal atmospheric wind speeds (<2 m/s (4.5 mph) with gusts up to 

20 m/s (44 mph). The test conditions for the bounding re-suspension rate of 4E-5/hr were based 

upon an aqueous slurry of submicron sized calcium molybdate stabilized with surfactant that was 

sprayed on the surface of a lightly vegetated area. Material re-suspended was collected by 

samplers and analyzed.

If one assumes that cleanup did not occur for about 4 days (100 hours), the fraction of the 

deposited release that could become airborne by re-suspension would be 4E-3 (ARR of 4E-5/hr 

times 100 hrs). 

Sehmel (as cited in USDOE 1994, I:4.101) also reported a bounding re-suspension rate of 1E2/passage based on passage of vehicles through solid particles of ZnS <25 mm in diameter 

deposited on an asphalt road. The re-suspension value decreases rapidly over time and are about 

an order of magnitude after four days of aging (USDOE 1994, I:4.102). 

B. Data from CCPS Vapor Cloud Modeling “Aerosol Project”

For this work, the term “aerosol” means any liquid not falling to the ground within a short 

distance of the point of release. The Center for Chemical Process Safety (CCPS) aerosol 

research activities resulted in field tests conducted in 1989 for releases of superheated water from 

a storage tank through a release orifice, (Woodard 1995; Johnson and Woodward 1999). Water 

releases involved storage temperatures from 105 - 215 oC (378 to 488 K) corresponding to 

pressures at release orifice of 26.7 to 310 psia. The storage tank was pressurized with nitrogen 

pad to insure that fluid state at the release orifice was 100% liquid. The orifice was located 4 

foot (1.33 m) above a 50-foot (15.2 m) capture system designed to collect any liquid falling to 

the ground and direct the liquid to collection and weighing vessels. Capture pans were 50 foot 

long and 20 foot wide in five 10-foot long segments. The entire storage tank and capture system 

was enclosed in a greenhouse to shield the equipment from effects of the wind. 
21

Tests were also made for chlorine, CFC-11, methylamine, and myclohexane. Chlorine and CFC11 are gases. Methylamine is a highly volatile chemical (vapor pressure = 300 mm Hg) and 

myclohexane is less volatile (vapor pressure = 95 mm Hg) compared to water (vapor pressure = 

24 mm Hg). Airborne fraction results for water and myclohexane are summarized below and are 

based on 49 data runs for water (Johnson and Woodward 1999, p. 13-15) and 20 data runs for 

myclohexane (Johnson and Woodward 1999, p. 28) each liquid. The fraction airborne was 

calculated from the reported fraction captured. (100 - % captured)/100 = fraction airborne. The 

aerosol drop diameter sizes for water and myclohexane for the experiments were found in 

Woodward 1995, p. 13, and Woodward 1995, p. 130-131, respectively. 

Water & Cyclohexane Mass Fraction Airborne and Aerosol Diameter 

From CCPS “Aerosol Project”

Liquid Mass 

fraction 

airborne 

Aerosol 

diameter, 

μm

Water 0.03 - 0.54 54 - 440

Cyclohexane 0.36 - 0.94 148 - 630
22

VIII. References

Ballinger, M.Y., S.L. Sutter and W.H. Hodgson. May 1987. New Data for Aerosols Generated 

by Releases of Pressurized Powders and Solutions in Static Air. NUREG/CR-4779 (PNL)-6065), 

Pacific Northwest Laboratory, Richland, WA 99352. 

Code of Federal Regulations (CFR). July 1, 2009. Title 40, Section 302.4, Table 302.4 – List of 

Hazardous Substances and Reportable Quantities. See footnotes at end of table.

Federal Register, November 17, 1986. 51 FR 41570 and 41580.

Federal Register, April 22, 1987. 52 FR 13378

Jellinek, Schwartz & Connolly, Inc. August 31, 1999. Request to Delist Paraquat Dichloride 

From the California Accidental Release Program Under the Phase Two Rulemaking. Submitted 

by Zeneca Ag Products, Wilmington DE. Attachment: Appendix A, Worst-Case Release 

Analysis.

Johnson, D.W. and Woodward, J.L. 1999. RELEASE- A Model with Data to Predict Aerosol 

Rainout in Accidental Release. A CCPS Concept Book. Center for Chemical Process Safety 

CCPS). American Institute for Chemical Engineers, New York, NY.

Macnab, J.I. August 15, 2001. An Estimation of the Vapor Pressure of Paraquat Dichloride at 

its Decomposition Point. Syngenta Crop Protection.

Reiss, Richard. July 31, 2002. Estimation of an Aerosol Release Amount for Aqueous Solutions 

in an Accidental Release. Sciences International, Inc. Alexandra, VA 

Syngenta Crop Protection, Inc. August 30, 2001. Letter from Heather C. Winett Regarding 

Requested Delisting of Paraquat Dichloride from SARA Title III, Section 302; Zeneca Ag 

Products Inc. v. U.S. EPA. With Attachments number 1, 2, 4, 5, 6, 7 of 8 Total Attachments.

Attachment 1. USEPA. 1997. Reregistration Eligibility Decisions (RED) for Paraquat 

Dichloride, US Environmental Protection Agency, Office of Pesticide Programs, Special Review 

and Reregistration Divison, Washington, DC. http://www.epa.gov/oppsrrd1/REDs/0262red.pdf

Attachment 2. Table 1. OPP Restricted Use Pesticides Included and Not Included on the 

EPCRA List of Extremely Hazardous Substances.

Attachment 4. Process Flow Diagram for Paraquat Process. Syngenta Crop Protection, Inc., 

Bayport Plant, Pasadena, TX.

Attachment 5. August 29, 2001 Letter from Peter L. Gray of McKenna & Cuneo, L.L.P. 

Washington, DC regarding Huls America Inc. vs Carol Browner 1996 court decision, to Heather 
23

C. Winnett, Syngenta Crop Protection, Inc. Legal Group, Washington, DC.

Attachment 6. Paraquat Shipment Analysis. January 2000-February 2001.

Attachment 7. Technical Information for Paraquat Dichloride- Label Information, Technical 

Description, Material Safety Data Sheet for Gramoxone Max.

Syngenta Crop Protection, Inc. September 25, 2001. Letter to Kathleen Franklin, USPEA from 

Heather C. Winett Regarding Requested Delisting of Paraquat Dichloride from SARA Title III, 

Section 302; Zeneca Ag Products Inc. v. U.S. EPA. With Attachments number 3 and 8 of 8 

Total Attachments.

Attachment 3. Chemicals Classified as “Solids in Solution” on EPCRA 302 List with a 

Vapor Pressure Equal to or Lower than Paraquat Dichloride. Submitted with September 25, 

2001 letter to Kathleen Franklin, USEPA from Heather C. Winnett, Syngenta Crop Protection, 

Inc. Legal Group, Washington, DC.

Attachment 8. Summary of Incident History (Referenced in August 2001 Response to 

Question 11).

Woodward, J.L. 1995. Aerosol Drop Size Correlation and Corrected Rainout Data Using 

Models of Drop Evaporation, Pool Absorption and Pool Evaporation. In: International 

Conference and Workshop on Modeling and Mitigation the Consequences of Accidental 

Releases of Hazardous Materials, September 1995. New York: American Institute for Chemical 

Engineers Center for Chemical Process Safety, pp. 117-147.

USDOE. 1994. DOE Handbook, Airborne Release Fractions/Rates and Respirable Fractions 

for Nonreactor Nuclear Facilities. Volume I- Analysis of Experimental Data and Volume IIAppendices. December 1994. US Department of Energy, Washington, DC 20585 DOEHDBK-3010-94. 

http://www.hss.doe.gov/nuclearsafety/ns/techstds/standard/hdbk3010/h3010v1.pdf

http://www.hss.doe.gov/nuclearsafety/ns/techstds/standard/hdbk3010/h3010v2.pdf

USEPA. November 7, 1986. Technical Support Document for Determination of Levels of 

Concern. US Environmental Protection Agency, Office of Solid Waste and Emergency 

Response, Office of Emergency Management, Washington, DC. Public Docket 300PQ, 

Document No. 300PQ-2-12. 

USEPA. 1987a. Threshold Planning Quantities Technical Support Document. US 

Environmental Protection Agency, Office of Solid Waste and Emergency Response, Office of 

Emergency Management, Washington, DC. Public Docket 300PQ, Document No. 300PQ-2-21.

( April 7, 1987)

USEPA. 1987b. Chemicals That Were Assigned Threshold Planning Quantities Different From 
24

the Calculated Index Value. US Environmental Protection Agency, Office of Solid Waste and 

Emergency Response, Office of Emergency Management, Washington, DC. Public Docket 

300PQ, Document No. 300PQ-2-19 (April 7, 1987). 

USEPA. 1987c. Reactive Solids Whose Threshold Planning Quantities Should Be Less than 10, 

000 Pounds. US Environmental Protection Agency, Office of Solid Waste and Emergency 

Response, Office of Emergency Management, Washington, DC. Public Docket 300PQ, 

Document No. 300PQ-2-20 (April 7, 1987). 

USEPA. 1987d. Changes Made to Threshold Planning Quantities Between Proposed Rule and 

Final Rule. US Environmental Protection Agency, Office of Solid Waste and Emergency 

Response, Office of Emergency Management, Washington, DC. Public Docket 300PQ, 

Document No. 300PQ-22 (April 7, 1987). 

USEPA. 1995. AP-42 Emission Factors, Fifth Edition, Volume I. Chapter 13 Miscellaneous 

Dust Source. 13.2 Introduction to Fugitive Dust Sources. USEPA, Office of Air Quality 

Planning and Standards. http://www.epa.gov/ttn/chief/ap42/ch13/final/c13s02.pdf

USEPA. November 21, 2003. Letter from Michael O. Leavitt, Administrator, USEPA to Peter 

L. Gray of McKenna, Long and Aldridge L.L.P. regarding EPA‟s reconsideration of the petition 

submitted by Syngenta (formerly known as Zeneca, formerly known as ICI Americas) with 

respect to the chemical paraquat dichloride. US Environmental Protection Agency, Office of 

Solid Waste and Emergency Response, Office of Emergency Management, Washington, DC.

USPEA. 2004. Air Quality Criteria for Particulate Matter. Volume I and II. US

Environmental Protection Agency, Office of Research and Development, National Center for 

Environmental Assessment. Research Triangle Park, NC. EPA/600/P-99/002aF and 

EPA/600/P-99/002bF. 

http://oaspub.epa.gov/eims/eimscomm.getfile?p_download_id=435945

http://oaspub.epa.gov/eims/eimscomm.getfile?p_download_id=435946

USEPA. June 2009. Peer Review of Technical Support Document for Revised TPQ Method for 

EHS Solids in Solution. US Environmental Protection Agency, Office of Solid Waste and 

Emergency Response, Office of Emergency Management, Washington, DC. 4 attachments

Attachment 1. USPEA. February 2008. Revised TPQ Method for EHS Solids in 

Solution. US Environmental Protection Agency, Office of Solid Waste and Emergency 

Response, Office of Emergency Management, Washington, DC.

Attachment 2. USEPA. February 2008. Literature Survey for Liquid Aerosol Release 

Data to Support Revised TPQ Methodology for EHS Solids in Solution. US Environmental 

Protection Agency, Office of Solid Waste and Emergency Response, Office of Emergency 

Management, Washington, DC.
25

Attachment 3. USEPA. February 2008. Assigning Threshold Planning Quantities 

(TPQs) for Extremely Hazardous Substances. US Environmental Protection Agency, Office of 

Solid Waste and Emergency Response, Office of Emergency Management, Washington, DC.

Attachment 4. USEPA. February 4, 2008. List of 157 EHS Solid Substances with current 

TPQ and proposed effective TPQs. US Environmental Protection Agency, Office of Solid 

Waste and Emergency Response, Office of Emergency Management, Washington, DC.

Zeneca Inc. December 15, 1999. Paraquat Dichloride and the Emergency Planning and 

Community Right-to-Know Act of 1986. Presentation to USEPA‟s Chemical Emergency 

Preparedness and Prevention Office on behalf of Zeneca Inc. (Zeneca Ag Products). (Zeneca 

1999)

Zeneca Ag Products Inc. vs. Christine Todd Whitman and US Environmental Protection Agency. 

2000. Case No. 1:00CSV02434., United Stated District Court for the District of Columbia. 
26

APPENDIX A: Assigning Threshold Planning Quantities (TPQs) for Extremely Hazardous 

Substances

This data is presented to explain how the existing TPQs were developed for the EHS list in 1987 

for purposes of illustration and historical context. It does not reflect the proposed change in TPQ 

methodology for EHS solids in solution.

Ranking and TPQ Assignments

The threshold planning quantities were developed based on a ranking approach. The ranking 

was based on an index of toxicity, physical state, and potential for the chemical to become 

airborne. Chemicals with the highest index rank were assigned a threshold planning quantity of 

10,000 pounds. Chemicals with an index lower than 0.001 were assigned a TPQ of one. 

Between one and 10,000 pounds, chemicals were assigned to intermediate categories of 10, 100, 

500 or 1000 pounds, based on the order of magnitude of index range (see table below).

 Index Range and Assigned TPQs

 

Index Value Index Value TPQ 

(lbs)

< 1E-3(< 0.001) 1

≥ 1E-3 to < 1E-2(≥ 0.001 to < 0.01) 10

≥ 1E-2 to < 1E-1(≥ 0.01 to < 0.1) 100

≥ 1E-1 to < 1 E0(≥ 0.1 to < 1) 500

≥ 1E0 to < 1E+1 ≥ 1 to < 10 1,000

≥ 1E+2 ≥ 10 10,000

Index Value

The index was equal to Level of Concern (g/m3) divided by V where V is the extent to which the 

chemical can become airborne. The more toxic the chemical (lower level of concern), the lower 

the index, and thus, the lower the threshold is. Inversely, the lower the boiling point (the more 

volatile), the higher the V (thepotential to become airborne) and thus, the lower the index is.

Level of Concern

The Level of Concern (LOC) was equal to the Immediately Dangerous to Life and Health 

(IDLH) levels in grams/cubic meter, published by the National Institute of Occupational Safety 

and Health (NIOSH), available at the time of the rulemaking in 1986/1987. For substances 

without a published IDLH level, the LOC was estimated from acute animal toxicity test data as 

follows with inhalation data preferable to other data, and median lethality data preferable to other 

types. 
27

LOC equals: LC50 x 0.1 or 

LCLO or

LD50 x 0.01 or

LDLO x 0.1

LC50 is the Lethal Concentration 50% or the concentration of chemical in air at which 50% of the 

test animals died. LCLO is the Lethal Concentration Low or lowest concentration of the chemical 

in air (g/m3 ) at which any test animals died. 

LD50 is the Lethal Dose 50% or the dose of the chemical (mg/kg) that killed 50% of the test 

animals. LDLO is the Lethal Dose Low or the lowest dose of chemical (mg/kg) at which any test 

animals died. 

Determination of Potential Airborne Dispersion

1. For a chemical that is gaseous at ambient conditions:

V=1, assumes that all the chemical released will be dispersed to air.

2. For a chemical that is a liquid at ambient conditions:

V= 1.6 M0.67 / (T + 273), where

M= molecular weight 

T= boiling point in degrees C. 

V= G/Q = rate of volatilization (mass vaporized per time) per mass of liquid spilled. 

Assumes spill is 1 cm deep and has density of water.

3 For a chemical that is a reactive solid:

V=1. The solid chemical is defined as reactive if its NFPA reactivity rating is 2, 3, or 4.

4. For a chemical that is a non-reactive solid and:

a. In powder form with particle size of equal to or greater than 100 microns, The TPQ is set 

to the highest value of 10,000 pounds. Not likely to become airborne beyond facility‟s fenceline.

b. In powder form with particle size of less than 100 microns, V=1. Assumes that all the 

chemical released will be dispersed to air.

c. In molten form, V=1. However, amount molten should be multiplied by 0.3 to obtain the 

actual amount to be compared to the TPQ for reporting. 

Basis on these TPQ assignments, non-reactive solids will have two listed TPQs, 10,000 pounds 

and a lower assigned TPQ when it is in the form where V=1.
28

APPENDIX B: Comparison of Current TPQ (Volatilization) vs Effective TPQ (Aerosolization)

163 Liquid Extremely Hazardous Substances: Sorted by Index

CAS # Chemical Name

Mol.

Wt. (°C) V

Level of 

Concern 

(g/m3) Index

Current

TPQ

V = 1 

Index

V = 1 

TPQ

ARF=0.2 

Eff. TPQ

TPQ > 

Eff. TPQ

13463393 Nickel Carbonyl 171 43 0.159 7.0E-06 4.4E-05 1 7.0E-06 1 5 0

106967 Propargyl Bromide 119 88 0.109 2.9E-04 2.7E-03 10 2.9E-04 1 5 1

107448 Sarin 140 147 0.104 5.0E-04 4.8E-03 10 5.0E-04 1 5 1

541253 Lewisite 207 190 0.123 6.0E-04 4.9E-03 10 6.0E-04 1 5 1

359068 Fluoroacetyl Chloride 96 73 0.098 4.9E-04 5.0E-03 10 4.9E-04 1 5 1

77816 Tabun 162 240 0.094 4.7E-04 5.0E-03 10 4.7E-04 1 5 1

371620 Ethylene Fluorohydrin 64 103.5 0.069 3.5E-04 5.0E-03 10 3.5E-04 1 5 1

51752 Mechlorethamine 156 200 0.100 5.0E-04 5.0E-03 10 5.0E-04 1 5 1

78944 Methyl Vinyl Ketone 70 81.4 0.078 7.0E-04 9.0E-03 10 7.0E-04 1 5 1

298022 Phorate 260 290 0.118 1.1E-03 9.3E-03 10 1.1E-03 10 50 0

675149 Cyanuric Fluoride 135 73 0.124 1.7E-03 1.4E-02 100 1.7E-03 10 50 1

77474 Hexachlorocyclopentadiene 273 239 0.134 2.0E-03 1.5E-02 100 2.0E-03 10 50 1

30674807 Methacryloyloxyethyl Isocyanate 155 74 0.135 2.7E-03 2.0E-02 100 2.7E-03 10 50 1

2540821 Formothion 257 250 0.126 2.7E-03 2.1E-02 100 2.7E-03 10 50 1

1558254 Trichloro(Chloromethyl)Silane 184 118 0.135 3.0E-03 2.2E-02 100 3.0E-03 10 50 1

542881 Chloromethyl Ether 115 106 0.101 2.5E-03 2.5E-02 100 2.5E-03 10 50 1

13171216 Phosphamidon 300 350 0.117 3.0E-03 2.6E-02 100 3.0E-03 10 50 1

107302 Chloromethyl Methyl Ether 81 59 0.091 4.5E-03 4.9E-02 100 4.5E-03 10 50 1

54115 Nicotine 162 246.7 0.093 4.6E-03 4.9E-02 100 4.6E-03 10 50 1

56382 Parathion 291 375 0.111 5.5E-03 5.0E-02 100 5.5E-03 10 50 1

78002 Tetraethyllead 323 110 0.201 1.0E-02 5.0E-02 100 1.0E-02 100 500 0

12108133

Manganese, 

TricarbonylMethylcyclopetadienyl 218 232 0.117 5.9E-03 5.0E-02 100 5.9E-03 10 50 1
29

APPENDIX B: Comparison of Current TPQ (Volatilization) vs Effective TPQ (Aerosolization)

163 Liquid Extremely Hazardous Substances: Sorted by Index

CAS # Chemical Name

Mol.

Wt. (°C) V

Level of 

Concern 

(g/m3) Index

Current

TPQ

V = 1 

Index

V = 1 

TPQ

ARF=0.2 

Eff. TPQ

TPQ > 

Eff. TPQ

75741 Tetramethyllead 267 110 0.177 8.9E-03 5.0E-02 100 8.9E-03 10 50 1

55914 Isofluorphate 184 185 0.115 5.8E-03 5.0E-02 100 5.8E-03 10 50 1

597648 Tetraethyltin 235 181 0.137 6.9E-03 5.0E-02 100 6.9E-03 10 50 1

13463406 Iron, Pentacarbonyl- 196 103 0.146 8.0E-03 5.5E-02 100 8.0E-03 10 50 1

920467 Methacryloyl Chloride 105 96 0.098 6.0E-03 6.1E-02 100 6.0E-03 10 50 1

98077 Benzotrichloride 195 220.8 0.111 7.0E-03 6.3E-02 100 7.0E-03 10 50 1

152169 Diphosphoramide, Octamethyl- 286 330 0.117 8.0E-03 6.8E-02 100 8.0E-03 10 50 1

50782699

Phosphonothioic Acid, Methyl-,S-

(2-(Bis(1-Methylethyl) 

Amino)Ethyl)O-Ethyl Ester 267 298 0.118 8.6E-03 7.3E-02 100 8.6E-03 10 50 1

555771 Tris(2-Chloroethyl)Amine 205 256 0.107 8.0E-03 7.5E-02 100 8.0E-03 10 50 1

7550450 Titanium Tetrachloride 190 136.4 0.131 1.0E-02 7.6E-02 100 1.0E-02 100 500 0

107493 TEPP 290 310 0.123 1.0E-02 8.2E-02 100 1.0E-02 100 500 0

13071799 Terbufos 288 315 0.121 1.1E-02 9.1E-02 100 1.1E-02 100 500 0

91087 Toluene 2,6-Diisocyanate 174 245 0.098 9.0E-03 9.2E-02 100 9.0E-03 10 50 1

814686 Acrylyl Chloride 91 75 0.094 9.0E-03 9.6E-02 100 9.0E-03 10 50 1

141662 Dicrotophos 237 400 0.093 9.0E-03 9.7E-02 100 9.0E-03 10 50 1

505602 Mustard Gas 159 215 0.098 1.0E-02 1.0E-01 500 1.0E-02 100 500 0

115264 Dimefox 154 210 0.097 1.0E-02 1.0E-01 500 1.0E-02 100 500 0

19624227 Pentaborane 63 60 0.077 8.0E-03 1.0E-01 500 8.0E-03 10 50 1

4098719 Isophorone Diisocyanate 222 350 0.096 1.2E-02 1.3E-01 500 1.2E-02 100 500 0

944229 Fonofos 246 380 0.098 1.3E-02 1.3E-01 500 1.3E-02 100 500 0

75796 Methyltrichlorosilane 149 67 0.135 1.8E-02 1.3E-01 500 1.8E-02 100 500 0

110009 Furan 68 32 0.089 1.2E-02 1.4E-01 500 1.2E-02 100 500 0
30

APPENDIX B: Comparison of Current TPQ (Volatilization) vs Effective TPQ (Aerosolization)

163 Liquid Extremely Hazardous Substances: Sorted by Index

CAS # Chemical Name

Mol.

Wt. (°C) V

Level of 

Concern 

(g/m3) Index

Current

TPQ

V = 1 

Index

V = 1 

TPQ

ARF=0.2 

Eff. TPQ

TPQ > 

Eff. TPQ

107028 Acrolein 56 52.5 0.073 1.1E-02 1.6E-01 500 1.1E-02 100 500 0

60344 Methyl Hydrazine 46 87.5 0.058 9.4E-03 1.6E-01 500 9.4E-03 10 50 1

108985 Thiophenol 110 168.3 0.085 1.4E-02 1.7E-01 500 1.4E-02 100 500 0

2587908

Phosphorothioic Acid, O,ODimethyl-S-(2-Methylthio) Ethyl 

Ester 216 230 0.117 2.0E-02 1.7E-01 500 2.0E-02 100 500 0

1122607 Nitrocyclohexane 129 205.5 0.087 1.5E-02 1.7E-01 500 1.5E-02 100 500 0

4835114

Hexamethylenediamine, N,N'-

Dibutyl- 228 205 0.127 2.2E-02 1.7E-01 500 2.2E-02 100 500 0

8065483 Demeton 258 300 0.115 2.0E-02 1.7E-01 500 2.0E-02 100 500 0

78342 Dioxathion 457 250 0.185 3.4E-02 1.8E-01 500 3.4E-02 100 500 0

79221 Methyl Chloroformate 95 71 0.098 1.9E-02 1.9E-01 500 1.9E-02 100 500 0

7783702 Antimony Pentafluoride 217 141 0.142 2.7E-02 1.9E-01 500 2.7E-02 100 500 0

115902 Fensulfothion 308 440 0.104 2.0E-02 1.9E-01 500 2.0E-02 100 500 0

298044 Disulfoton 274 400 0.102 2.0E-02 2.0E-01 500 2.0E-02 100 500 0

78717 Oxetane, 3,3-Bis(Chloromethyl)- 155 200 0.099 2.0E-02 2.0E-01 500 2.0E-02 100 500 0

140761 Pyridine, 2-Methyl-5-Vinyl- 119 181 0.087 1.9E-02 2.2E-01 500 1.9E-02 100 500 0

115219 Trichloroethylsilane 164 97.9 0.131 3.0E-02 2.3E-01 500 3.0E-02 100 500 0

98873 Benzal Chloride 161 205 0.101 2.3E-02 2.3E-01 500 2.3E-02 100 500 0

24017478 Triazofos 313 350 0.121 2.8E-02 2.3E-01 500 2.8E-02 100 500 0

57578 Propiolactone, Beta- 72 162 0.065 1.5E-02 2.3E-01 500 1.5E-02 100 500 0

1622328

Ethanesulfonyl Chloride, 2-

Chloro- 163 200 0.103 2.5E-02 2.4E-01 500 2.5E-02 100 500 0

10025873 Phosphorus Oxychloride 153 106 0.123 3.0E-02 2.4E-01 500 3.0E-02 100 500 0
31

APPENDIX B: Comparison of Current TPQ (Volatilization) vs Effective TPQ (Aerosolization)

163 Liquid Extremely Hazardous Substances: Sorted by Index

CAS # Chemical Name

Mol.

Wt. (°C) V

Level of 

Concern 

(g/m3) Index

Current

TPQ

V = 1 

Index

V = 1 

TPQ

ARF=0.2 

Eff. TPQ

TPQ > 

Eff. TPQ

75785 Dimethyldichlorosilane 129 70 0.121 3.0E-02 2.5E-01 500 3.0E-02 100 500 0

3689245 Sulfotep 322 310 0.132 3.5E-02 2.7E-01 500 3.5E-02 100 500 0

98135 Trichlorophenylsilane 212 201.5 0.122 3.3E-02 2.7E-01 500 3.3E-02 100 500 0

78535 Amiton 269 330 0.113 3.3E-02 2.9E-01 500 3.3E-02 100 500 0

2524030

Dimethyl 

Phosphorochloridothioate 161 180 0.106 3.2E-02 3.0E-01 500 3.2E-02 100 500 0

2497076 Oxydisulfoton 274 330 0.114 3.5E-02 3.1E-01 500 3.5E-02 100 500 0

76028 Trichloroacetyl Chloride 182 118 0.134 4.5E-02 3.4E-01 500 4.5E-02 100 500 0

88051 Aniline, 2,4,6-Trimethyl- 135 232 0.085 2.9E-02 3.4E-01 500 2.9E-02 100 500 0

297972 Thionazin 248 360 0.102 3.5E-02 3.4E-01 500 3.5E-02 100 500 0

696286 Phenyl Dichloroarsine 223 254.4 0.114 4.0E-02 3.5E-01 500 4.0E-02 100 500 0

7786347 Mevinphos 224 280 0.109 4.0E-02 3.7E-01 500 4.0E-02 100 500 0

21548323 Fosthietan 241 250 0.121 4.7E-02 3.9E-01 500 4.7E-02 100 500 0

126987 Methacrylonitrile 67 90.3 0.074 3.0E-02 4.1E-01 500 3.0E-02 100 500 0

998301 Triethoxysilane 164 132 0.121 5.0E-02 4.1E-01 500 5.0E-02 100 500 0

98168

Benzenamine, 3-

(Trifluoromethyl)- 161 187.5 0.105 4.4E-02 4.2E-01 500 4.4E-02 100 500 0

107073 Chloroethanol 81 128 0.075 3.3E-02 4.4E-01 500 3.3E-02 100 500 0

107119 Allylamine 57 55 0.073 3.2E-02 4.4E-01 500 3.2E-02 100 500 0

7726956 Bromine 160 60 0.144 6.5E-02 4.5E-01 500 6.5E-02 100 500 0

1464535 Diepoxybutane 86 138 0.077 3.5E-02 4.5E-01 500 3.5E-02 100 500 0

110576 Trans-1,4-Dichlorobutene 125 155.5 0.095 4.4E-02 4.6E-01 500 4.4E-02 100 500 0

919868 Demeton-S-Methyl 230 305 0.106 5.0E-02 4.7E-01 500 5.0E-02 100 500 0

760930 Methacrylic Anhydride 154 240 0.091 4.5E-02 4.9E-01 500 4.5E-02 100 500 0
32

APPENDIX B: Comparison of Current TPQ (Volatilization) vs Effective TPQ (Aerosolization)

163 Liquid Extremely Hazardous Substances: Sorted by Index

CAS # Chemical Name

Mol.

Wt. (°C) V

Level of 

Concern 

(g/m3) Index

Current

TPQ

V = 1 

Index

V = 1 

TPQ

ARF=0.2 

Eff. TPQ

TPQ > 

Eff. TPQ

80637 Methyl 2-Chloroacrylate 121 140 0.096 5.0E-02 5.2E-01 500 5.0E-02 100 500 0

786196 Carbophenothion 343 350 0.128 6.8E-02 5.3E-01 500 6.8E-02 100 500 0

111693

Isopropylmethylpyrazolyl 

Dimethylcarbamate 211 295 0.102 5.6E-02 5.5E-01 500 5.6E-02 100 500 0

140294 Benzyl Cyanide 117 233.5 0.077 4.3E-02 5.6E-01 500 4.3E-02 100 500 0

77781 Dimethyl Sulfate 126 188 0.089 5.0E-02 5.6E-01 500 5.0E-02 100 500 0

100447 Benzyl Chloride 127 179 0.091 5.2E-02 5.7E-01 500 5.2E-02 100 500 0

509148 Tetranitromethane 196 126 0.138 8.0E-02 5.8E-01 500 8.0E-02 100 500 0

107120 Propionitrile 55 97.2 0.063 3.7E-02 5.8E-01 500 3.7E-02 100 500 0

79210 Peracetic Acid 76 105 0.077 4.5E-02 5.8E-01 500 4.5E-02 100 500 0

594423 Perchloromethylmercaptan 186 147 0.126 7.6E-02 6.0E-01 500 7.6E-02 100 500 0

624839 Methyl Isocyanate 57 39 0.077 4.7E-02 6.1E-01 500 4.7E-02 100 500 0

27137855 Trichloro(Dichlorophenyl)Silane 280 260 0.131 8.0E-02 6.1E-01 500 8.0E-02 100 500 0

3254635

Phosphoric Acid, Dimethyl 4-

(Methylthio) Phenyl Ester 248 300 0.112 7.0E-02 6.2E-01 500 7.0E-02 100 500 0

21923239 Chlorthiophos 361 400 0.123 7.8E-02 6.3E-01 500 7.8E-02 100 500 0

24934916 Chlormephos 235 295 0.109 7.0E-02 6.4E-01 500 7.0E-02 100 500 0

151564 Ethyleneimine 43 55 0.061 4.0E-02 6.6E-01 500 4.0E-02 100 500 0

538078 Ethylbis(2-Chloroethyl)Amine 170 200 0.106 7.5E-02 7.1E-01 500 7.5E-02 100 500 0

2665307

Phosphonothioic Acid, Methyl-

,O-(4-Nitrophenyl) O-Phenyl 

Ester 309 400 0.111 8.0E-02 7.2E-01 500 8.0E-02 100 500 0

584849 Toluene 2,4-Diisocyanate 174 251 0.097 7.0E-02 7.2E-01 500 7.0E-02 100 500 0

814493 Diethyl Chlorophosphate 173 210 0.104 8.0E-02 7.7E-01 500 8.0E-02 100 500 0
33

APPENDIX B: Comparison of Current TPQ (Volatilization) vs Effective TPQ (Aerosolization)

163 Liquid Extremely Hazardous Substances: Sorted by Index

CAS # Chemical Name

Mol.

Wt. (°C) V

Level of 

Concern 

(g/m3) Index

Current

TPQ

V = 1 

Index

V = 1 

TPQ

ARF=0.2 

Eff. TPQ

TPQ > 

Eff. TPQ

7784341 Arsenous Trichloride 181 130.2 0.129 1.0E-01 7.7E-01 500 1.0E-01 500 2500 0

3569571 Sulfoxide, 3-Chloropropyl Octyl 239 338 0.103 8.0E-02 7.8E-01 500 8.0E-02 100 500 0

470906 Chlorfenvinfos 360 390 0.124 1.0E-01 8.0E-01 500 1.0E-01 500 2500 0

327980 Trichloronate 334 360 0.124 1.0E-01 8.1E-01 500 1.0E-01 500 2500 0

2703131

Phosphonothioic Acid, Methyl-

,O-Ethyl,O-(4-(Methylthio) 

Phenyl) Ester 262 298 0.117 1.0E-01 8.6E-01 500 1.0E-01 500 2500 0

950107 Mephosfolan 269 410 0.100 9.0E-02 9.0E-01 500 9.0E-02 100 500 0

3735237 Methyl Phenkapton 349 400 0.120 1.1E-01 9.2E-01 500 1.1E-01 500 2500 0

7791233 Selenium Oxychloride 166 180 0.108 1.0E-01 9.2E-01 500 1.0E-01 500 2500 0

109615 Propyl Chloroformate 123 114 0.104 1.0E-01 9.6E-01 500 1.0E-01 500 2500 0

563122 Ethion 384 400 0.128 1.3E-01 1.0E+00 1000 1.3E-01 500 2500 0

107164 Formaldehyde Cyanohydrin 57 183 0.053 6.0E-02 1.1E+00 1000 6.0E-02 100 500 1

542767 Propionitrile, 3-Chloro- 90 175 0.073 9.0E-02 1.2E+00 1000 9.0E-02 100 500 1

23505411 Pirimifos-Ethyl 333 130 0.195 2.5E-01 1.3E+00 1000 2.5E-01 500 2500 0

7664939 Sulfuric Acid 98 290 0.061 8.0E-02 1.3E+00 1000 8.0E-02 100 500 1

10140871 Ethanol, 1,2-Dichloro-, Acetate 157 280 0.086 1.1E-01 1.3E+00 1000 1.1E-01 500 2500 0

558258 Methanesulfonyl Fluoride 98 124 0.087 1.4E-01 1.6E+00 1000 1.4E-01 500 2500 0

57147 Dimethylhydrazine 60 63.9 0.074 1.2E-01 1.7E+00 1000 1.2E-01 500 2500 0

75865 Acetone Cyanohydrin 85 200 0.066 1.2E-01 1.7E+00 1000 1.2E-01 500 2500 0

149746 Dichloromethylphenylsilane 191 205 0.113 2.0E-01 1.8E+00 1000 2.0E-01 500 2500 0

627112 Chloroethyl Chloroformate 143 155.7 0.104 2.0E-01 1.9E+00 1000 2.0E-01 500 2500 0

300629 Amphetamine 135 200 0.091 2.0E-01 2.2E+00 1000 2.0E-01 500 2500 0
34

APPENDIX B: Comparison of Current TPQ (Volatilization) vs Effective TPQ (Aerosolization)

163 Liquid Extremely Hazardous Substances: Sorted by Index

CAS # Chemical Name

Mol.

Wt. (°C) V

Level of 

Concern 

(g/m3) Index

Current

TPQ

V = 1 

Index

V = 1 

TPQ

ARF=0.2 

Eff. TPQ

TPQ > 

Eff. TPQ

7719122 Phosphorus Trichloride 137 76 0.124 2.8E-01 2.3E+00 1000 2.8E-01 500 2500 0

62737 Dichlorvos 221 400 0.088 2.0E-01 2.3E+00 1000 2.0E-01 500 2500 0

13194484 Ethoprophos 242 300 0.111 2.6E-01 2.4E+00 1000 2.6E-01 500 2500 0

353424

Boron Trifluoride Compound with 

Methyl Ether (1:1) 114 126 0.096 2.3E-01 2.4E+00 1000 2.3E-01 500 2500 0

2636262 Cyanophos 243 350 0.102 2.5E-01 2.5E+00 1000 2.5E-01 500 2500 0

302012 Hydrazine 32 113.5 0.042 1.1E-01 2.5E+00 1000 1.1E-01 500 2500 0

7722841

Hydrogen Peroxide (Conc > 

52%) 34 152 0.040 1.0E-01 2.6E+00 1000 1.0E-01 500 2500 0

119380 Adiponitrile 108 295 0.065 1.7E-01 2.6E+00 1000 1.7E-01 500 2500 0

110894 Piperidine 85 106 0.083 2.2E-01 2.7E+00 1000 2.2E-01 500 2500 0

62759 Nitrosodimethylamine 74 151 0.068 1.9E-01 2.8E+00 1000 1.9E-01 500 2500 0

78977 Lactonitrile 71 182 0.061 1.8E-01 2.9E+00 1000 1.8E-01 500 2500 0

78820 Isobutyronitrile 69 103.8 0.073 2.5E-01 3.4E+00 1000 2.5E-01 500 2500 0

7697372 Nitric Acid 63 83 0.072 2.6E-01 3.6E+00 1000 2.6E-01 500 2500 0

57749 Chlordane 410 400 0.134 5.0E-01 3.7E+00 1000 5.0E-01 500 2500 0

3037727

Silane, (4-

Aminobutyl)Diethoxymethyl- 205 220 0.115 4.5E-01 3.9E+00 1000 4.5E-01 500 2500 0

10476956 Methacrolein Diacetate 172 191 0.108 4.4E-01 4.1E+00 1000 4.4E-01 500 2500 0

106898 Epichlorohydrin 93 116.5 0.085 3.8E-01 4.5E+00 1000 3.8E-01 500 2500 0

75774 Trimethylchlorosilane 109 57 0.112 5.0E-01 4.5E+00 1000 5.0E-01 500 2500 0

62533 Aniline 93 184 0.073 3.8E-01 5.2E+00 1000 3.8E-01 500 2500 0

107186 Allyl Alcohol 58 97 0.066 3.6E-01 5.4E+00 1000 3.6E-01 500 2500 0

4170303 Crotonaldehyde 70 104 0.073 4.0E-01 5.5E+00 1000 4.0E-01 500 2500 0
35

APPENDIX B: Comparison of Current TPQ (Volatilization) vs Effective TPQ (Aerosolization)

163 Liquid Extremely Hazardous Substances: Sorted by Index

CAS # Chemical Name

Mol.

Wt. (°C) V

Level of 

Concern 

(g/m3) Index

Current

TPQ

V = 1 

Index

V = 1 

TPQ

ARF=0.2 

Eff. TPQ

TPQ > 

Eff. TPQ

123739 Crotonaldehyde, (E)- 70 104 0.073 4.0E-01 5.5E+00 1000 4.0E-01 500 2500 0

2238075 Diglycidyl Ether 130 260 0.078 4.5E-01 5.7E+00 1000 4.5E-01 500 2500 0

108054 Vinyl Acetate Monomer 86 72 0.092 5.4E-01 5.9E+00 1000 5.4E-01 500 2500 0

108236 Isopropyl Chloroformate 123 104.6 0.106 1.0E+00 9.4E+00 1000 1.0E+00 1000 5000 0

556649 Methyl Thiocyanate 73 130 0.070 8.5E-01 1.2E+01 10000 8.5E-01 500 2500 1

98953 Nitrobenzene 123 210.8 0.083 1.0E+00 1.2E+01 10000 1.0E+00 1000 5000 1

542905 Ethylthiocyanate 87 146 0.076 1.0E+00 1.3E+01 10000 1.0E+00 1000 5000 1

111444 Dichloroethyl Ether 143 178 0.099 1.5E+00 1.5E+01 10000 1.5E+00 1000 5000 1

75558 Propyleneimine 57 66 0.071 1.2E+00 1.6E+01 10000 1.2E+00 1000 5000 1

107131 Acrylonitrile 54 77.3 0.066 1.1E+00 1.7E+01 10000 1.1E+00 1000 5000 1

75150 Carbon Disulfide 76 46.5 0.091 1.6E+00 1.7E+01 10000 1.6E+00 1000 5000 1

108918 Cyclohexylamine 99 134.5 0.085 1.6E+00 1.8E+01 10000 1.6E+00 1000 5000 1

67663 Chloroform 119 61.7 0.118 4.9E+00 4.1E+01 10000 4.9E+00 1000 5000 1

75569 Propylene Oxide 58 34.23 0.079 4.8E+00 6.1E+01 10000 4.8E+00 1000 5000 1

107153 Ethylenediamine 60 116 0.064 4.9E+00 7.7E+01 10000 4.9E+00 1000 5000 1

Count = 47
36

APPENDIX C: EHS Solids TPQ Comparison

Extremely Hazardous Substances List: 157 Solids (Non-reactive)

Alphabetical name order V=1 Effective 

CAS # Chemical Name TPQ TPQ

1752303 Acetone Thiosemicarbazide 1000 5000

79061 Acrylamide 1000 5000

116063 Aldicarb 100 500

309002 Aldrin 500 2500

54626 Aminopterin 500 2500

3734972 Amiton Oxalate 100 500

1397940 Antimycin A 1000 5000

86884 ANTU 500 2500

1303282 Arsenic Pentoxide 100 500

1327533 Arsenous Oxide 100 500

2642719 Azinphos-Ethyl 100 500

86500 Azinphos-Methyl 10 50

98055 Benzenearsonic Acid 10 50

100141 Benzene, 1-(Chloromethyl)-4-Nitro- 500 2500

3615212 Benzimidazole, 4,5-Dichloro-2-(Trifluoromethyl)- 500 2500

15271417 Bicyclo[2.2.1]Heptane-2-Carbonitrile,5-Chloro6- ((((Methylamino)Carbonyl)Oxy)Imino)-,(1S-

(1-alpha, 2-beta,4-alpha,5-alpha,6E))-

500 2500

534076 Bis(Chloromethyl) Ketone 10 50

4044659 Bitoscanate 500 2500

28772567 Bromadiolone 100 500

1306190 Cadmium Oxide 100 500

2223930 Cadmium Stearate 1000 5000

7778441 Calcium Arsenate 500 2500

8001352 Camphechlor 500 2500

56257 Cantharidin 100 500

51832 Carbachol Chloride 500 2500

26419738 Carbamic Acid, Methyl-,O-(((2,4-Dimethyl-1,3-

Dithiolan- 2-Yl)Methylene)Amino)-

100 500

1563662 Carbofuran 10 50

999815 Chlormequat Chloride 100 500

79118 Chloroacetic Acid 100 500

3691358 Chlorophacinone 100 500

1982474 Chloroxuron 500 2500

10025737 Chromic Chloride 1 5

10210681 Cobalt Carbonyl 10 50

62207765 Cobalt,((2,2'-(1,2-

Ethanediylbis(Nitrilomethylidene)) Bis(6-

100 500
37

APPENDIX C: EHS Solids TPQ Comparison

Extremely Hazardous Substances List: 157 Solids (Non-reactive)

Alphabetical name order V=1 Effective 

CAS # Chemical Name TPQ TPQ

FluoroPhenolato))(2-)-N,N',O,O')-

64868 Colchicine 10 50

56724 Coumaphos 100 500

5836293 Coumatetralyl 500 2500

95487 Cresol, o- 1000 5000

535897 Crimidine 100 500

506683 Cyanogen Bromide 500 2500

506785 Cyanogen Iodide 1000 5000

66819 Cycloheximide 100 500

17702419 Decaborane(14) 500 2500

10311849 Dialifor 100 500

71636 Digitoxin 100 500

20830755 Digoxin 10 50

60515 Dimethoate 500 2500

99989 Dimethyl-p-Phenylenediamine 10 50

644644 Dimetilan 500 2500

534521 Dinitrocresol 10 50

88857 Dinoseb 100 500

1420071 Dinoterb 500 2500

82666 Diphacinone 10 50

514738 Dithiazanine Iodide 500 2500

541537 Dithiobiuret 100 500

316427 Emetine, Dihydrochloride 1 5

115297 Endosulfan 10 50

2778043 Endothion 500 2500

72208 Endrin 500 2500

2104645 EPN 100 500

50146 Ergocalciferol 1000 5000

379793 Ergotamine Tartrate 500 2500

22224926 Fenamiphos 10 50

4301502 Fluenetil 100 500

640197 Fluoroacetamide 100 500

144490 Fluoroacetic Acid 10 50

51218 Fluorouracil 500 2500

23422539 Formetanate Hydrochloride 500 2500

17702577 Formparanate 100 500

3878191 Fuberidazole 100 500

13450903 Gallium Trichloride 500 2500
38

APPENDIX C: EHS Solids TPQ Comparison

Extremely Hazardous Substances List: 157 Solids (Non-reactive)

Alphabetical name order V=1 Effective 

CAS # Chemical Name TPQ TPQ

123319 Hydroquinone 500 2500

297789 Isobenzan 100 500

102363 Isocyanic Acid,3,4-Dichlorophenyl Ester 500 2500

465736 Isodrin 100 500

21609905 Leptophos 500 2500

58899 Lindane 1000 5000

109773 Malononitrile 500 2500

1600277 Mercuric Acetate 500 2500

7487947 Mercuric Chloride 500 2500

21908532 Mercuric Oxide 500 2500

10265926 Methamidophos 100 500

950378 Methidathion 500 2500

2032657 Methiocarb 500 2500

16752775 Methomyl 500 2500

151382 Methoxyethylmercuric Acetate 500 2500

502396 Methylmercuric Dicyanamide 500 2500

1129415 Metolcarb 100 500

315184 Mexacarbate 500 2500

50077 Mitomycin C 500 2500

6923224 Monocrotophos 10 50

2763964 Muscimol 500 2500

65305 Nicotine Sulfate 100 500

991424 Norbormide 100 500

Organorhodium Complex (PMN-82-147) 10 50

630604 Ouabain 100 500

23135220 Oxamyl 100 500

1910425 Paraquat Dichloride 10 50

2074502 Paraquat Methosulfate 10 50

298000 Parathion-Methyl 10 50

12002038 Paris Green 500 2500

2570265 Pentadecylamine 100 500

108952 Phenol 500 2500

4418660 Phenol, 2,2'-Thiobis(4-Chloro-6-Methyl)- 100 500

64006 Phenol, 3-(1-Methylethyl)-Methylcarbamate 500 2500

58366 Phenoxarsine, 10,10'-Oxydi- 500 2500

59881 Phenylhydrazine Hydrochloride 1000 5000

62384 Phenylmercury Acetate 500 2500

2097190 Phenylsilatrane 100 500
39

APPENDIX C: EHS Solids TPQ Comparison

Extremely Hazardous Substances List: 157 Solids (Non-reactive)

Alphabetical name order V=1 Effective 

CAS # Chemical Name TPQ TPQ

103855 Phenylthiourea 100 500

4104147 Phosacetim 100 500

947024 Phosfolan 100 500

732116 Phosmet 10 50

57476 Physostigmine 100 500

57647 Physostigmine, Salicylate (1:1) 100 500

124878 Picrotoxin 500 2500

10124502 Potassium Arsenite 500 2500

2631370 Promecarb 500 2500

70699 Propiophenone, 4-Amino- 100 500

2275185 Prothoate 100 500

129000 Pyrene 1000 5000

504245 Pyridine, 4-Amino- 500 2500

1124330 Pyridine, 4-Nitro-, 1-Oxide 500 2500

53558251 Pyriminil 100 500

14167181 Salcomine 500 2500

7783008 Selenious Acid 1000 5000

563417 Semicarbazide Hydrochloride 1000 5000

7631892 Sodium Arsenate 1000 5000

7784465 Sodium Arsenite 500 2500

124652 Sodium Cacodylate 100 500

62748 Sodium Fluoroacetate 10 50

13410010 Sodium Selenate 100 500

10102188 Sodium Selenite 100 500

10102202 Sodium Tellurite 500 2500

900958 Stannane, Acetoxytriphenyl- 500 2500

57249 Strychnine 100 500

60413 Strychnine, Sulfate 100 500

10031591 Thallium Sulfate 100 500

6533739 Thallous Carbonate 100 500

7791120 Thallous Chloride 100 500

2757188 Thallous Malonate 100 500

7446186 Thallous Sulfate 100 500

2231574 Thiocarbazide 1000 5000

39196184 Thiofanox 100 500

79196 Thiosemicarbazide 100 500

5344821 Thiourea, (2-Chlorophenyl)- 100 500

614788 Thiourea, (2-Methylphenyl)- 500 2500
40

APPENDIX C: EHS Solids TPQ Comparison

Extremely Hazardous Substances List: 157 Solids (Non-reactive)

Alphabetical name order V=1 Effective 

CAS # Chemical Name TPQ TPQ

1031476 Triamiphos 500 2500

824113 Trimethylolpropane Phosphite 100 500

1066451 Trimethyltin Chloride 500 2500

639587 Triphenyltin Chlorid 500 2500

2001958 Valinomycin 1000 5000

1314621 Vanadium Pentoxide 100 500

81812 Warfarin 500 2500

129066 Warfarin Sodium 100 500

28347139 Xylylene Dichloride 100 500

58270089 Zinc, Dichloro(4,4-Dimethyl5((((Methylamino)Carbonyl) 

Oxy)Imino)Pentanenitrile)-, (T-4)-

100 500
41

APPENDIX D: Estimation of % Mass Aerosol vs. Diameter Size for Aerosol Releases

Pressure Venting Above the Liquid Level and Superheated Liquid Scenarios

This appendix explains how EPA estimated the mass fraction of aerosols with sizes less than 100 

microns for two scenarios: Pressure Venting Above the Liquid Level and Superheated Liquids.

Volume II of the 1994 DOE Handbook contains data tables for these two scenarios with the percent 

mass for aerosol size less than 10 microns. Using statistical analysis and data from Tables A-6, A-7 

and A-9, EPA determined the cumulative percent mass of aerosols that are below 100 μm. This 

statistical analysis involved using the median aerosol diameter and standard deviation provided in the 

tables to calculate the aerosol diameter at one standard deviation below and above the median 

diameter. The data was then graphed on log-normal paper to show aerosol diameter versus cumulative 

mass fraction. Then the mass fraction of aerosol that were less than 100 microns were read off the 

graph. The results (in % Mass) are provided in italics in the tables below which have the original data 

used in Tables A-6, A-7 (Pressure Venting Above the Liquid Level scenario), and A-9 (Superheated 

Liquid scenario).

Particle Size Distribution Produced by Pressurized Release of Uranine Solution

Original Data from Table A-6 in DOE Handbook

Source, 

cm3

Rep. Run psig Median diameter, 

um

σg %10 um 

and less

% 100 um 

and less

350 1 1 500 4 3 86 100

2 13 500 4.3 2.4 85 100

1 6 250 4 1.6 98 100

2 14 250 3.6 3 84 100

1 4 50 1.5 3 83 100

2 8 50 2.1 4 87 100

100 1 7 500 4 3 90 100

2 12 500 4.0 4 70 100

1 3 250 2.4 4 78 100

2 9 250 4 3.6 77 100

2 11 50 2.1 4 80 100
42

Particle Size Distribution Produced by Pressurized Release of UNH Solution

Original Data from Table A-7 in DOE Handbook

Source, 

cm3

Rep. Run psig Median diameter, 

um

σg %10 um 

and less

% 100 um 

and less

350 1 1 500 17 4.0 34 90

2 8 500 14 2.9 37 95

1 5 250 45 5.9 20 68

2 10 250 12 2.9 45 98

1 4 50 3 4.8 76 98.7

2 12 50 5 5.2 70 96.5

100 1 6 500 14 2.5 46 98.6

2 9 500 14 2.9 38 95.3

1 3 250 14 2.7 36 97.6

2 11 250 11 4.6 45 91

1 2 50 6 7.5 61 92

2 13 50 8 4.6 60 95

Particle Size Distribution Produced by Flashing Spray Release of Superheated Uranine Solution

Original Data from Table A-9 in DOE Handbook

Source, 

cm3

psig Median diameter, 

um

σg %10 um 

and less

% 100 um 

and less

700 125 5.9 2.6 78 100

350 240 6.2 2.7 73 100

125 7.7 2.7 66 100

60 8.4 5.6 62 93

100 125 6.4 3.3 69 100

Example Graph Using Median Diameter and Standard Deviation to Determine Size Distribution:

To demonstrate how the data was graphed and results read, one graph for one particular experiment 

from (Table A-7, Pressurized Releases of UNH, 500 psig, Run 1) is provided at the end of this 

Appendix. On the log-normal paper, aerosol size in microns is on the Y axis and the cumulative 

weight percent is on the X axis, so that the end of the X axis is 0.99 (~1) or almost 100%. The median 

aerosol diameter value, for example, 17 um, is plotted on the Y axis with the X axis position of 0.5, 

which represents the statistical median point. This means that 50% of aerosol release had aerosol 

diameters are greater than 17 um and 50% of the release had aerosol diameters of less than 17 um. For 

this particular set of example experimental data, the standard deviation is given as 4.0. Multiplying the 

median size of 17 um times 4.0 results in another aerosol size of 68 um. This Y value is plotted on the 

graph using an X axis value of 0.84, representing 84% or one standard deviation. 84% is the value of 

one standard deviation for a standard normal distribution. One standard deviation in the other 

direction, is 1- 0.84 or 0.16. Dividing the median 17 um) by 4.0, results in Y= 4.25 um, which can be 

plotted on the graph at the X = 0.16 value. After connecting the points by a line on the graph, the 
43

cumulative mass fraction can be read along the X axis and aerosol diameter size (um) is read along Y 

axis. Reading the graph at value of Y=100 microns, a mass fraction of X= 0.90 (or 90%) is found 

which correlates to aerosol size less (or equal to) 100 microns.
44