Hazardous Materials and Waste Management Division 

Air Screening Concentrations Table 

The Division has prepared a table listing indoor air remediation goals and action levels for a number of 

volatile organic compounds to be used at sites where vapor intrusion may be a concern. This was 

prompted in response to the U.S. Environmental Protection Agency having released a new assessment of 

the health effects of Trichloroethene (TCE), which was one of the most commonly used degreasing 

solvents. Existing air concentrations were also updated to incorporate the 2009 EPA risk assessment 

guidance for the inhalation pathway presented in Risk Assessment Guidance for Superfund (RAGS) Part 

F1

. Another notable change is the Division’s decision to adopt EPA’s June 2003 OSWER directive for 

Tetrachloroethene (PCE) (OSWER No. 9285.7-75) 

These new air screening concentration table values replace those that may be present in other older 

guidance documents, such as Table 1 found in the March 2006 “Dry Cleaner Remediation Guidance 

Document.” With the release of this new table, the Division hereby withdraws the use of both the August 

20, 2004 and August 17, 2006 interim risk evaluation and management policies for TCE and PCE, 

respectively. 

Development and quality checking of the numbers listed in the Air Screening Concentrations Table will 

be an ongoing process and readers are encouraged to report any errors that may be discovered to the 

Division. Please be sure to consult the footnotes to the table when using these table values. 

If you have questions about the derivation or application of these table values, please contact the Division 

by email sent to comments.hmwmd@state.co.us. Please be sure to put "Avramenko" in the subject line. 

1 U.S. EPA (2009). Risk Assessment Guidance for Superfund Volume I: Human Health Evaluation 

Manual (Part F, Supplemental Guidance for Inhalation Risk Assessment). OSWER 9285.7-82; January 

2009. Office of Superfund Remediation and Technology Innovation. EPA, Washington D.C. 
Air Screening Concentrations 

Volatile organic compounds are chemicals that have a high vapor pressure (molecular weight < 200 g/mol and Henry’s Law 

Constant > 10-5 atm m3

/ mol) and easily form vapors at normal temperature and pressure. This definition applies to a large 

number of organic compounds, many of which are manufactured chemicals. From this long list of chemicals, the Department 

has chosen those typically found in the environment at chemical release sites. 

The analytical method presently being used to determine the concentrations of VOCs in indoor air is the Compendium Method 

TO-15, selected ion monitoring (SIM) mode, as specified in EPA document EPA/625/R-96/010b using the specific Colorado 

Guidance for Analysis of Indoor Air Samples (April 2000) (http://www.cdphe.state.co.us/hm/airsmpl.pdf). The laboratory must 

demonstrate to the Department its ability to perform this analysis with quantitatively reliable results down to levels that equate 

to health-based concentrations for the chemicals of concern. 

Target indoor air concentrations for those chemicals not included on this list may be found in the EPA Regional Screening 

Level table. Always check for the most recent version of the EPA Regional Screening Level table, the link to which is: 

http://www.epa.gov/reg3hwmd/risk/human/rb-concentration_table/Generic_Tables/pdf/master_sl_table_bwrun_NOV2011.pdf

Chemical 

Abstracts 

No. 

Chemical Name 

(IUPAC) 

Risk Basis 

C=Cancer 

NC=Noncancer 

Residential 

Remediation 

Goal1 

(R=10-6, HQ=1) 

μg/m3

Residential 

Action Level 

(R=10-5, HQ=1) 

ug/m3

Worker6

Remediation 

Goal 

(R=10-6, HQ=1) 

ug/m3

Worker6

Action Level 

(R=10-5, HQ=1) 

ug/m3

71-43-2 Benzene C1 0.31 3.1 1.6 16.0 

56-23-5 Carbon tetrachloride C1 0.41 4.1 2.0 20.0 

108-90-7 Chlorobenzene NC2 52 52 220 220 

67-66-3 Chloroform C1 0.11 1.1 0.53 5.3 

95-50-1 1,2-dichlorobenzene NC3 210 210 880 880 

106-46-7 1,4-dichlorobenzene C4 0.22 2.2 1.1 11 

107-34-3 1,1-dichloroethane C4 1.5 15 7.7 77 

107-06-2 1,2-dichloroethane C1 0.094 0.94 0.47 4.7 

75-35-4 1,1-dichloroethene NC5 7.3 7.3 30.1 30.1 

156-59-2 Cis-1,2-dichloroethene -- No value* No value* No value* No value* 

78-87-5 1,2-dichloropropane C4 0.24 2.4 1.2 12 

100-41-4 Ethylbenzene C4 0.97 9.7 4.9 49 

75-09-2 Methylene chloride C1 5.2 52 26 260 

100-42-5 Styrene NC1 1,000 1,000 4,400 4,400 

79-34-5 1,1,2,2-Tetrachloroethane C4 0.042 0.42 0.21 2.1 

127-18-4 Tetrachloroethene C4 0.41 4.1 2.1 21 

108-88-3 Toluene NC1 5200 5200 22,000 22,000 

71-55-6 1,1,1-Trichloroethane NC1 5200 5200 22,000 22, 000 

79-00-5 1,1,2-Trichloroethane -- 0.15 ( C1) 0.21 (NC2) 0.77 ( C1) 0.88 (NC2) 

79001-6 Trichloroethene -- 0.43 ( C1) 2.1 (NC1) 3.0 (C1) 8.8 (NC1)

75-01-4 Vinyl chloride C1 0.16 1.6 2.8 28 

1330-20-7 Xylenes (Mixture/Total) NC1 100 100 440 440 

Note: Indoor air target concentrations based on non-carcinogenic risk correspond to a hazard quotient (HQ) of 1. For facilities where 

multiple non-carcinogenic chemicals are present, HQ values should be divided by a factor of 10 to account for additivity. If adjusted table 

values are exceeded, consultation with a toxicologist is recommended to assess likely impact on specific target organs. 

*- Currently, no toxicity value is available for the inhalation pathway. Please contact the Department for additional information on a sitespecific basis. 

IUPAC – International Union of Pure and Applied Chemistry 

1

 Source of toxicity value: EPAIRIS; 2 Source of toxicity value: EPA PPRTV; 3 Source of toxicity value: EPA HEAST 4

 Source of toxicity value: Cal EPA; 5 Source of toxicity value: CDPHE 6 Worker values are considered protective for indoor office workers with occasional contact with outdoor soil, and for outdoor workers 

engaged in light to moderate activity. Values are NOT APPLICABLE to outdoor workers routinely engaged in contact-intensive activity. 

For facilities where contact intensive use is anticipated, additional analysis and consultation with a toxicologist will be required to determine 

appropriate site-specific inputs to the risk equations. 

The screening values are derived from a variety of sources. Parties using this table should periodically check these sources to verify that the 

posted values are still in use. 

December 15, 2011 Version 
Application of Screening Levels for Carcinogens 

Example of Tetrachloroethene (PCE) 

Risk Range Action Required

Residential 

Use 

Air (μg/m3

) 

Worker 

Use 

Air (μg/m3

) 

Less than or equal to 

1x10-6 or background 

No Further Action, measures to 

reduce PCE concentrations in air 

not required 

≤ 0.41 ≤ 2.1 

Between 1x10-6 and 

1x10-5

Provided soil and/or ground water 

contamination is being remediated 

as approved by the Department, 

continued monitoring of indoor air 

is likely unnecessary. 

0.41 to 4.10 2.1 to 21 

Greater than 1x10-5

Further study needed to determine 

whether or not the source is from 

subsurface releases. Mitigation is 

required it is determined that the 

vapors are derived from a 

subsurface source. 

> 4.1 > 21 

Application of Screening Levels for Mixed Cancer and Noncancer Effects 

Example of Trichloroethene (TCE) 

Risk Range Action Required Residential Use 

Air (μg/m3

) 

Worker Use 

Air (μg/m3) 

Less than or equal to 

1x10-6 or background 

No Further Action, measures to 

reduce TCE concentrations in air 

not required 

≤ 0.43 ≤ 3.0 

Between 1x10-6 (cancer) 

and HI=1 (noncancer) 

Provided soil and/or ground water 

contamination is being remediated 

as approved by the Department, 

continued monitoring of indoor air 

is likely unnecessary. 

0.43 to 2.1 3.0 to 8.8 

Greater than HI=1 

Further study needed to determine 

whether or not the source is from 

subsurface releases. Mitigation is 

required it is determined that the 

vapors are derived from a 

subsurface source. 

> 2.1 > 8.8 
Application of Screening Levels for Non-Carcinogens 

Example of 1,1-Dichloroethene (1,1-DCE) 

Risk Range Action Required Residential Use 

Air (μg/m3

) 

Worker Use 

Air (μg/m3) 

Less than or equal to 

HQI=1 or background 

No Further Action, measures to 

reduce 1,1-DCE concentrations in 

air not required 

≤ 7.3 ≤ 30.1 

Greater than HQI=1 

Further study needed to determine 

whether or not the source is from 

subsurface releases. Mitigation is 

required it is determined that the 

vapors are derived from a 

subsurface source 

> 7.3 > 30.1 

For sites with multiple contaminants or exposure pathways, cleanup levels should result in a cumulative 

hazard quotient equal to or less than one for all those constituents with similar critical endpoints. 

For sites with multiple contaminants, cleanup levels should be set so that the risk posed by individual 

constituents does not exceed a 1x10-6 and where the cumulative (total) excess upper bound lifetime risk 

from all contaminants does not exceed a 1x10-5. 

In all cases, further analysis may be warranted if an action level is exceeded that would trigger the need to 

mitigate exposures, particularly if it is believed that the constituents are derived from sources other than 

what may be present in soil or ground water. In these cases, lines of evidence should be examined to 

determine whether the observed concentrations are from a subsurface source or background 

(activities/products within the structure being sampled). If the lines of evidence indicate a subsurface 

source, the Division will require remedial actions to mitigate exposure. A discussion on conducting a 

line of evidence analysis may be found in Section 4.1 of the CDPHE’s September 2004 Draft Indoor Air 

Guidance (http://www.cdphe.state.co.us/hm/indoorair.pdf) and Section 3.7.3 of ITRC’s January 2007 

Vapor Intrusion Pathway: A Practical Guideline (http://www.itrcweb.org/Documents/VI-1.pdf).