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1

2

3

4

5

6

7 IMMEDIATELY DANGEROUS TO LIFE OR HEALTH (IDLH) VALUE PROFILE

8

9

10

11 FOR

12

13

14

15 BUTANE

16

17

18

19 [CAS NO. 106-97-8] 

20

21

22

23

24

25

26 Department of Health and Human Services 

27 Centers for Disease Control and Prevention 

28 National Institute for Occupational Safety and Health 

29

30
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1 Disclaimer

2

3 Mention of any company or product does not constitute endorsement by the National Institute for Occupational 

4 Safety and Health (NIOSH). In addition, citations to Web sites external to NIOSH do not constitute NIOSH 

5 endorsement of the sponsoring organizations or their programs or products. Furthermore, NIOSH is not 

6 responsible for the content of these Web sites. 

7

8 Ordering Information 

9

10 To receive this document or information about other occupational safety and health topics, contact NIOSH: 

11

12 Telephone: 1-800-CDC-INFO (1-800-232-4636) 

13 TTY: 1-888-232-6348 

14 E-mail: cdcinfo@cdc.gov 

15 Or visit the NIOSH Web site: www.cdc.gov/niosh 

16

17 For a monthly update on news at NIOSH, subscribe to NIOSH eNews by visiting www.cdc.gov/niosh/eNews. 

18

19 DHHS (NIOSH) Publication No. XXX 

20

21
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1 Foreword 

2 Chemicals are a ubiquitous component of the modern workplace. Occupational exposures to chemicals have the 

3 potential to adversely affect the health and lives of workers. Acute or short-term exposures to high concentrations 

4 of some airborne chemicals have the ability to quickly overwhelm workers, resulting in a spectrum of undesirable 

5 health outcomes that may inhibit the ability to escape from the exposure environment (e.g., irritation of the eyes 

6 and respiratory tract or cognitive impairment), cause severe irreversible effects (e.g., damage to the respiratory 

7 tract or reproductive toxicity), and in extreme cases, cause death. Airborne concentrations of chemicals capable 

8 of causing such adverse health effects or of impeding escape from high-risk conditions may arise from a variety of 

9 non-routine workplace situations , including special work procedures (e.g., in confined spaces), industrial 

10 accidents (e.g., chemical spills or explosions), and chemical releases into the community (e.g., during 

11 transportation incidents or other uncontrolled-release scenarios). 

12

13 The “immediately dangerous to life or health air concentration values (IDLH values)” developed by the National 

14 Institute for Occupational Safety and Health (NIOSH) characterize these high-risk exposure concentrations and 

15 conditions [NIOSH 2013]. IDLH values are based on a 30-minute exposure duration and have traditionally 

16 served as a key component of the decision logic for the selection of respiratory protection devices [NIOSH 2004]. 

17 Occupational health professionals have employed these values beyond their initial purpose as a component of the 

18 NIOSH Respirator Selection Logic to assist in developing Risk Management Plans for non-routine work practices 

19 governing operations in high-risk environments (e.g., confined spaces) and the development of Emergency 

20 Preparedness Plans. 

21

22 The approach used to derive IDLH values for high priority chemicals is outlined in the NIOSH Current 

23 Intelligence Bulletin (CIB) 66: Derivation of Immediately Dangerous to Life or Health Values [NIOSH 2013]. 

24 CIB 66 provides 1) an update on the scientific basis and risk assessment methodology used to derive IDLH 

25 values, 2) the rationale and derivation process for IDLH values, and 3) a demonstration of the derivation of 

26 scientifically credible IDLH values using available data resources. 

27

28 The purpose of this technical report is to present the IDLH value for butane (CAS # 106-97-8). The scientific 

29 basis, toxicologic data and risk assessment approach used to derive the IDLH value are summarized to ensure 

30 transparency and scientific credibility. 

31

32 John Howard, M.D. 

33 Director 

34 National Institute for Occupational Safety and Health 
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1 Centers for Disease Control and Prevention
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1 Table of Contents

2 FOREWORD ................................................................................................................................................................ III

3 ABBREVIATIONS .......................................................................................................................................................VI

4 GLOSSARY .................................................................................................................................................................VII

5 ACKNOWLEDGMENTS ..............................................................................................................................................X

6 1.0 INTRODUCTION.............................................................................................................................................. 1

7 1.1 OVERVIEW OF THE IDLH VALUE FOR BUTANE...........................................................................................................1

8 1.2 PURPOSE .....................................................................................................................................................................1

9 1.3 GENERAL SUBSTANCE INFORMATION ......................................................................................................................1

10 2.0 ANIMAL TOXICITY DATA............................................................................................................................. 4

11 3.0 HUMAN DATA ................................................................................................................................................. 7

12 4.0 SUMMARY........................................................................................................................................................ 7

13 5.0 REFERENCES......................................................................................................................................................... 8

14

15
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1 Abbreviations 

2

3 ACGIH American Conference of Governmental Industrial Hygienists 

4 AEGL Acute Exposure Guideline Levels 

5 AIHA American Industrial Hygiene Association 

6 BMC benchmark concentration 

7 BMCL benchmark concentration lower confidence limit 

8 C ceiling 

9 CAS chemical abstract service 

10 ERPG Emergency Response Planning Guidelines 

11 IDLH immediately dangerous to life or health 

12 LC50 median lethal concentration 

13 LCLo lowest concentration of a chemical that caused death in humans or animals 

14 LEL lower explosive limit 

15 LOAEL lowest observed adverse effect level 

mg/m3 16 milligram(s) per cubic meter 

17 NAC National Advisory Committee 

18 NAS National Academy of Sciences 

19 NIOSH National Institute for Occupational Safety and Health 

20 NOAEL no observed adverse effect level 

21 OSHA Occupational Safety and Health Administration 

22 PEL permissible exposure limit 

23 ppm parts per million 

24 RD50 concentration of a chemical in the air that is estimated to cause a 50% decrease in the respiratory 

25 rate 

26 REL recommended exposure limit 

27 SCP Standard Completion Program 

28 STEL short term exposure limit 

29 TLV threshold limit value 

30 TWA time weighted average 

31 UEL upper explosive limit 

32 WEEL workplace environmental exposure level 
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1 Glossary

2

3 Acute Exposure: Exposure by the oral, dermal, or inhalation route for 24 hours or less. 

4 Acute Exposure Guideline Levels (AEGLs): Threshold exposure limits for the general public applicable to 

5 emergency exposure periods ranging from 10 minutes to 8 hours. AEGL-1, AEGL 2, and AEGL-3 are 

6 developed for five exposure periods (10 and 30 minutes, 1 hour, 4 hours, and 8 hours) and are distinguished 

7 by varying degrees of severity of toxic effects ranging from transient, reversible effects to life-threatening 

8 effects [NAS 2001]. AEGLs are intended to be guideline levels used during rare events or single once-in-a9 lifetime exposures to airborne concentrations of acutely toxic, high-priority chemicals [NAS 2001]. The 

10 threshold exposure limits are designed to protect the general population, including the elderly, children or 

11 other potentially sensitive groups that are generally not considered in the development of workplace exposure 

12 recommendations (additional information available at http://www.epa.gov/oppt/aegl/). 

13 Acute Reference Concentration (RfC): An estimate (with uncertainty spanning perhaps an order of magnitude) 

14 of a continuous inhalation exposure for an acute duration (24 hours or less) of the human population 

15 (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a 

16 lifetime. It can be derived from a NOAEL, LOAEL, or benchmark concentration, with uncertainty factors 

17 (UFs) generally applied to reflect limitations of the data used. Generally used in USEPA noncancer health 

18 assessments [USEPA 2014]. 

19 Acute Toxicity: Any poisonous effect produced within a short period of time following an exposure, usually 24 

20 to 96 hours. 

21 Adverse Effect: A substance-related biochemical change, functional impairment, or pathologic lesion that affects 

22 the performance of an organ or system or alters the ability to respond to additional environmental challenges. 

23 Benchmark Dose/Concentration (BMD/BMC): A dose or concentration that produces a predetermined change 

24 in response rate of an effect (called the benchmark response, or BMR) compared to background [USEPA 

25 2014] (additional information available at http://www.epa.gov/ncea/bmds/). 

26 Benchmark Response (BMR): A predetermined change in response rate of an effect. Common defaults for the 

27 BMR are 10% or 5%, reflecting study design, data variability, and sensitivity limits used. 

28 BMCL: A statistical lower confidence limit on the concentration at the BMC [USEPA 2014]. 

29 Bolus Exposure: A single, relatively large dose. 

30 Ceiling Value (“C”): U.S. term in occupational exposure indicating the airborne concentration of a potentially 

31 toxic substance that should never be exceeded in a worker’s breathing zone. 

32 Chronic Exposure: Repeated exposure for an extended period of time. Typically exposures are more than 

33 approximately 10% of life span for humans and >90 days to 2 years for laboratory species. 

34 Critical Study: The study that contributes most significantly to the qualitative and quantitative assessment of risk 

35 [USEPA 2014]. 

36

37 Dose: The amount of a substance available for interactions with metabolic processes or biologically significant 

38 receptors after crossing the outer boundary of an organism [USEPA 2014]. 

39 ECt50: A combination of the effective concentration of a substance in the air and the exposure duration that is 

40 predicted to cause an effect in 50% (one half) of the experimental test subjects. 
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1 Emergency Response Planning Guidelines (ERPGs): Maximum airborne concentrations below which nearly all 

2 individuals can be exposed without experiencing health effects for 1-hour exposure. ERPGs are presented in a 

3 tiered fashion with health effects ranging from mild or transient to serious, irreversible, or life threatening 

4 (depending on the tier). ERPGs are developed by the American Industrial Hygiene Association [AIHA 2006]. 

5 Endpoint: An observable or measurable biological event or sign of toxicity ranging from biomarkers of initial 

6 response to gross manifestations of clinical toxicity. 

7 Exposure: Contact made between a chemical, physical, or biological agent and the outer boundary of an 

8 organism. Exposure is quantified as the amount of an agent available at the exchange boundaries of the 

9 organism (e.g., skin, lungs, gut). 

10 Extrapolation: An estimate of the response at a point outside the range of the experimental data, generally 

11 through the use of a mathematical model, although qualitative extrapolation may also be conducted. The 

12 model may then be used to extrapolate to response levels that cannot be directly observed. 

13 Hazard: A potential source of harm. Hazard is distinguished from risk, which is the probability of harm under 

14 specific exposure conditions. 

15 Immediately Dangerous to Life or Health (IDLH) condition: A situation that poses a threat of exposure to 

16 airborne contaminants when that exposure is likely to cause death or immediate or delayed permanent adverse 

17 health effects or prevent escape from such an environment [NIOSH 2004, 2013]. 

18 IDLH value: A maximum (airborne concentration) level above which only a highly reliable breathing apparatus 

19 providing maximum worker protection is permitted [NIOSH 2004, 2013]. IDLH values are based on a 30-

20 minute exposure duration. 

21 LC01: The statistically determined concentration of a substance in the air that is estimated to cause death in 1% of 

22 the test animals. 

23 LC50: The statistically determined concentration of a substance in the air that is estimated to cause death in 50% 

24 (one half) of the test animals; median lethal concentration. 

25 LCLO: The lowest lethal concentration of a substance in the air reported to cause death, usually for a small 

26 percentage of the test animals. 

27

28 LD50: The statistically determined lethal dose of a substance that is estimated to cause death in 50% (one half) of 

29 the test animals; median lethal concentration. 

30 LDLO: The lowest dose of a substance that causes death, usually for a small percentage of the test animals. 

31 LEL: The minimum concentration of a gas or vapor in air, below which propagation of a flame does not occur in 

32 the presence of an ignition source. 

33 Lethality: Pertaining to or causing death; fatal; referring to the deaths resulting from acute toxicity studies. May 

34 also be used in lethality threshold to describe the point of sufficient substance concentration to begin to cause 

35 death. 

36 Lowest Observed Adverse Effect Level (LOAEL): The lowest tested dose or concentration of a substance that 

37 has been reported to cause harmful (adverse) health effects in people or animals. 
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1 Mode of Action: The sequence of significant events and processes that describes how a substance causes a toxic 

2 outcome. Mode of action is distinguished from the more detailed mechanism of action, which implies a more 

3 detailed understanding on a molecular level. 

4 No Observed Adverse Effect Level (NOAEL): The highest tested dose or concentration of a substance that has 

5 been reported to cause no harmful (adverse) health effects in people or animals. 

6 Occupational Exposure Limit (OEL): Workplace exposure recommendations developed by governmental 

7 agencies and non-governmental organizations. OELs are intended to represent the maximum airborne 

8 concentrations of a chemical substance below which workplace exposures should not cause adverse health 

9 effects. OELs may apply to ceiling, short-term (STELs), or time-weighted average (TWA) limits. 

10 Peak Concentration: Highest concentration of a substance recorded during a certain period of observation. 

11 Permissible Exposure Limit (PEL): Occupational exposure limits developed by OSHA (29 CFR 1910.1000) or 

12 MSHA (30 CFR 57.5001) for allowable occupational airborne exposure concentrations. PELs are legally 

13 enforceable and may be designated as ceiling, STEL, or TWA limits. 

14

15 Point of Departure (POD): The point on the dose–response curve from which dose extrapolation is initiated. 

16 This point can be the lower bound on dose for an estimated incidence or a change in response level from a 

17 concentration-response model (BMC), or it can be a NOAEL or LOAEL for an observed effect selected from 

18 a dose evaluated in a health effects or toxicology study. 

19 RD50: The statistically determined concentration of a substance in the air that is estimated to cause a 50% (one 

20 half) decrease in the respiratory rate. 

21 Recommended Exposure Limit (REL): Recommended maximum exposure limit to prevent adverse health 

22 effects based on human and animal studies and established for occupational (up to 10-hour shift, 40-hour 

23 week) inhalation exposure by NIOSH. RELs may be designated as ceiling, STEL, or TWA limits. 

24 Short-Term Exposure Limit (STEL): A worker’s 15-minute time-weighted average exposure concentration that 

25 shall not be exceeded at any time during a work day. 

26 Target Organ: Organ in which the toxic injury manifests in terms of dysfunction or overt disease. 

27 Threshold Limit Values (TLVs®): Recommended guidelines for occupational exposure to airborne 

28 contaminants, published by the American Conference of Governmental Industrial Hygienists (ACGIH). TLVs 

29 refer to airborne concentrations of chemical substances and represent conditions under which it is believed 

30 that nearly all workers may be repeatedly exposed, day after day, over a working lifetime, without adverse 

31 effects. TLVs may be designated as ceiling, short-term (STELs), or 8-hr TWA limits. 

32 Time-Weighted Average (TWA): A worker’s 8-hour (or up to 10-hour) time-weighted average exposure 

33 concentration that shall not be exceeded during an 8-hour (or up to 10-hour) work shift of a 40-hour week. 

34 The average concentration is weighted to take into account the duration of different exposure concentrations. 

35 Toxicity: The degree to which a substance is able to cause an adverse effect on an exposed organism. 

36

37 Uncertainty Factors (UFs): Mathematical adjustments applied to the POD when developing IDLH values. The 

38 UFs for IDLH value derivation are determined by considering the study and effect used for the POD, with 

39 further modification based on the overall database. 
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1 Workplace Environmental Exposure Levels (WEELs): Exposure levels developed by the American Industrial 

2 Hygiene Association (AIHA) that provide guidance for protecting most workers from adverse health effects 

3 related to occupational chemical exposures expressed as a TWA or ceiling limit.

4

5

6

7

8 Acknowledgments 

9

10 This document was developed by the Education and Information Division (Paul Schulte, Ph.D., Director). G. 

11 Scott Dotson, Ph.D., was the project officer and lead NIOSH author for this technical report. The basis for this 

12 document was a report contracted by NIOSH and prepared by Andrew Maier, Ph.D., Ann Parker, and Lynn 

13 Haber, Ph.D. (Toxicology Excellence for Risk Assessment [TERA]). 

14

15 Education and Information Division 

16 Devin Baker, M.Ed. 

17 Charles L. Geraci, Ph.D. 

18 Thomas J. Lentz, Ph.D. 

19 Richard Niemeier, Ph.D. 

20 Chris Sofge, Ph.D. 

21

22 NIOSH would like to acknowledge the contribution of the following subject matter experts for their critical 

23 technical review of this report. 

24

25 Mary A. Fox, Ph.D., Assistant Professor; Co-Director, Risk Sciences and Public Policy Institute; 

26 Department of Health Policy and Management, Bloomberg School of Public Health, Johns Hopkins 

27 University 

28

29 Richard B. Schlesinger, Ph.D., Fellow A.T.S., Senior Associate Dean for Academic Affairs and Research 

30 Professor of Biology, Dyson College of Arts and Sciences, Pace University 

31 
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1 1.0 Introduction 

2 1.1 Overview of the IDLH Value for Butane 

3

4 IDLH Value: 1,400 ppm (>10% LEL) 

5

6 Basis for IDLH Value: Despite the availability of toxicity data capable of being used to calculate health-based 

7 estimates for butane (see Tables 4 and 5), these estimates are all greater than 10% of the lower explosive limit 

8 (>10% LEL). NIOSH has adopted a threshold of 10% LEL as a default basis for the IDLH value based on 

9 explosivity concerns [NIOSH 2014]. Safety considerations related to the potential hazard of explosion must be 

10 taken into account and the IDLH value is set at the 10% LEL for butane of 1,400 ppm. 

11 1.2 Purpose 

12

13 This IDLH Value Profile presents (1) a brief summary of technical data associated with acute inhalation 

14 exposures to butane and (2) the rationale behind the Immediately Dangerous to Life or Health (IDLH) value for 

15 butane. IDLH values are developed based on the scientific rationale and logic outlined in the NIOSH Current 

16 Intelligence Bulletin (CIB) 66: Derivation of Immediately Dangerous to Life or Health (IDLH) Values [NIOSH 

17 2013]. As described in CIB 66, NIOSH performs in-depth literature searches to ensure that all relevant data from 

18 human and animal studies with acute exposures to the substance are identified. Information included in CIB 66 on 

19 the literature search includes pertinent databases, key terms, and guides for evaluating data quality and relevance 

20 for the establishment of an IDLH value. The information that is identified in the in-depth literature search is 

21 evaluated with general considerations that include description of studies (i.e., species, study protocol, exposure 

22 concentration and duration), health endpoint evaluated, and critical effect levels (e.g., NOAELs, LOAELs, LC50

23 values). For butane, the in-depth literature search was conducted through February 2014. 

24

25 1.3 General Substance Information 

26

27 Chemical; Butane

28 CAS No: 106-97-8 

29 Synonyms: Butane, pure; n-Butane; Methylethylmethane; Diethyl; Liquefied petroleum gas (LPG); Butyl 

30 hydride* 

Chemical category: Aliphatic, saturated hydrocarbons; Organic gases† 31
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1

2 Structural formula: 

3

4

5

6 Table 1 highlights selected physiochemical properties of butane relevant to IDLH conditions. Table 2 provides 

7 alternative exposure guidelines for butane. Table 3 summaries the Acute Exposure Guidelines Level (AEGL) 

8 values for butane. 

9

10 Table 1: Physiochemical Properties of Butane 

11

Property Value 

Molecular weight 58.12‡

Chemical formula C4H10

Description Colorless gas 

Odor Gasoline-like; Natural gas

Odor Threshold none§

UEL 9.4%†

LEL 1.4%†

Vapor pressure 1820 mmHg at 25°C (77°F)‡

Flash point -60°C (-76°F)‡

Ignition temperature 287.78°C (550°F)‡

Solubility Practically insoluble in water†

Abbreviation: oC – Celsius; o 12 F – Fahrenheit; mmHg – millimeter mercury; LEL – lower explosive limit; UEL – upper explosive limit * 13 AIHA [1989] 

† 14 IFA [2013] 

‡ 15 HSDB [2013] 

16

17

18 Table 2: Alternative Exposure Guidelines for Butane 

19

Organization Value 

Original (SCP) IDLH value None

NIOSH REL 800 ppm (1,900 mg/m3

), TWA

OSHA PEL [2011] 800 ppm (1,900 mg/m3

), TWA

ACGIH TLV [2014] 1,000 ppm (2,370 mg/m3

), STEL

AIHA ERPG [2010] Not available

AIHA WEEL [2010] Not available 

20 Abbreviation: ACGIH – American Conference of Governmental Industrial Hygienists; AIHA – American Industrial Hygiene 

21 Association; ERPG – Emergency Response Preparedness Guidelines; IDLH – immediately dangerous to life or health; NIOSH – National 

22 Institute for Occupational Safety and Health; OSHA – Occupational Safety and Health Administration; PEL – permissible exposure limit; 

23 REL – recommended exposure limit; SCP – Standards Completion Program; STEL - short term exposure limit; WEEL – workplace 

24 environmental exposure level

H3C

CH3
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1 Table 3: AEGL Values for Butane 

2

Classification 10-min 30-min 1-hour 4-hour 8-hour Endpoint [AEGL-1 * 6,900 ppm†

16,000 mg/m3

5,500 ppm†

13,000 mg/m3

5,500 ppm†

13,000 mg/m3

5,500 ppm†

13,000 mg/m3

Drowsine[Patty and 

AEGL-2 ** * * * * Dazed app

[Nuckolls 

AEGL-3 **   **  ** LC01 in m

[Shugaev 

Abbreviation: AEGL – acute exposure guideline levels; mg/m3 3 – milligrams per cubic meter; min – minute; ppm – parts per million 

4 References: NAS [2008] 5 † = >10% LEL 6 * = >50% LEL; ** = >100% LEL
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1 2.0 Animal Toxicity Data 

2

3 The available toxicokinetic data on butane [Gill et al. 1991] and propane [Stewart et al. 1977] indicate steady4 state plasma concentrations for butane are achieved within 30 minutes of exposure. By analogy to other CNS 

5 depressants, concentration is expected to be the primary determinant of the observed effects, consistent with the 

6 choice of n = 3 for extrapolation from durations longer than 30 minutes. 

7

8 Lethal concentrations of butane were evaluated in rats and mice. Shugaev [1969] reported LC50 values of 278,000 

9 ppm in rats exposed to butane for 4 hours, and 287,000 ppm in mice exposed for 2 hours. No other signs of 

10 toxicity were reported. Several studies evaluated acute toxicity under static conditions; these studies were not 

11 considered appropriate for derivation of an IDLH value. 

12

13 Non-lethal animal data of classical endpoints were limited to a single study. In guinea pigs, Nuckolls [1933] 

14 observed irregular and rapid breathing in animals exposed to 21,000 ppm for 2 hours, which escalated to retching 

15 and a dazed appearance at 50,000 ppm for 2 hours. Although the animals were able to walk, this exposure was 

16 considered potentially escape-impairing. Furthermore, although this is an older study, exposure concentrations 

17 were monitored and adjusted to maintain the nominal exposure levels. Other studies found that butane is a 

18 cardiac sensitizer [Chenowith 1946; Krantz et al. 1948] and can cause hemodynamic effects (decreased cardiac 

19 output, decreased ventricular or aortic pressure) [Zakhari 1977], but these studies were not considered appropriate 

20 for IDLH value derivation due to the limited details and exposure under anesthesia. 

21

22 Table 4 summarizes the LC data identified in animal studies and provides 30-minute equivalent derived values for 

23 butane. Table 5 provides non-lethal data reported in animal studies with 30-minute equivalent derived values. 

24 Information in these tables includes species of test animals, toxicological metrics (i.e., LC, BMCL, NOAEL, 

25 LOAEL), adjusted 30-minute concentration, and the justification for the composite uncertainty factors applied to 

26 calculate the derived values. 

27

28 
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1 Table 4: Lethal Concentration Data for Butane2

Reference Species 

(reference) 

LC50

(ppm) 

Other Lethality (ppm) 

Time (min) 

Adjusted 30-min Concentration* (ppm) 

Composite Uncertainty Factor 

Derived Value (ppm)†

Shugaev [1969] Mouse 287,000 -- 120 382,667 30 12,755Shugaev [1969] Mouse 278,000 -- 240 741,333 30 24,711 

34 Abbreviation: LC – lethal concentration; LC50 – median lethal concentration; LCLo – lowest concentration of a chemical that caused death in humans or a5 per million 6

* For exposures other than 30 minutes the ten Berge et al. [1986] relationship is used for duration adjustment (Cn 7 x t = k); no empirically est

8 available, therefore the default values were used, n = 3 for exposures greater than 30 minutes and n = 1 for exposures less than 30 minutes. 

† 9 The derived value is the result of the adjusted 30-minute concentration divided by the composite uncertainty factor. ± 10 Composite uncertainty factor to account for adjustment of LC50 values to LC01 values, use of lethal concentration threshold in animals, inte

11 human variability. 

^ 12 Composite uncertainty factor to account for use of lethal concentration threshold in animals, interspecies differences and human variability

1314
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1 Table 5: Non-lethal Concentration Data for Butane 

2

Reference Species 

(reference) 

NOAEL (ppm) 

LOAEL (ppm) 

Time (min) 

Adjusted 30-min Concentration* (ppm) 

Composite Uncertainty Factor 

Derived Value (ppm)†

Nuckolls [1933] Guinea Pig -- 50,000 120 66,667 10 6,667 Patty and Yant [1929] Human 10,000 -- 10 3,333 1 3,333 

3 Abbreviation: NOAEL – no observed adverse effect level; min – minute; LOAEL – lowest observed adverse effect level; ppm – parts per million4

* For exposures other than 30 minutes the ten Berge et al. [1986] relationship is used for duration adjustment (Cn 5 x t = k); no empirically est

6 available, therefore the default values were used, n = 3 for exposures greater than 30 minutes and n = 1 for exposures less than 30 minutes. 

† 7 The derived value is the result of the adjusted 30-minute concentration divided by the composite uncertainty factor. ± 8 Composite uncertainty factor to account for interspecies differences and human variability.‡ 9 Composite uncertainty factor to account for adjustment from a severe effect threshold in humans and human variability. 
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1 3.0 Human Data 

2

3 Although there are a number of case reports on lethality in humans from exposure to butane, none of the available 

4 studies provided information on exposure levels. In the only human study reporting exposure concentrations, 

5 Patty and Yant [1929] reported no symptoms except drowsiness in individuals that were exposed up to 1% butane 

6 concentrations (10,000 ppm) for 10 minutes. 

7 4.0 Summary 

8

9 Despite the availability of toxicity data capable of being used to calculate health-based estimates for butane (see 

10 Tables 4 and 5), these estimates are all are greater than 10% of the lower explosive limit (>10% LEL). NIOSH 

11 has adopted a threshold of 10% LEL as a default basis for the IDLH values based on explosivity concerns 

12 [NIOSH 2014]. Safety considerations related to the potential hazard of explosion must be taken into account and 

13 the IDLH value is set at the 10% LEL for butane of 1,400 ppm. 

14

15 If the explosive hazards of butane are controlled or toxicity issues are the primary concern, a health-based IDLH 

16 value could be derived from numerous datasets. The lowest LC50 value identified was 287,000 ppm for 2 hours in 

17 mice [Shugaev 1969]. The duration adjusted LC50 value for a 30-minute exposure is 382,700 ppm. An 

18 uncertainty factor of 30 would be applied to account for extrapolation from a concentration that is lethal to 

19 animals, animal to human differences and human variability, resulting in a potential IDLH value of 13,000 ppm. 

20 However, a more appropriate study from which to base the IDLH value is available. A LOAEL for signs of 

21 disorientation and toxicity was identified in guinea pigs exposed to 50,000 ppm for 2 hours [Nuckolls 1933]. The 

22 duration adjusted LOAEL for a 30-minute exposure is 66,700 ppm. An uncertainty factor of 10 is applied to 

23 account for extrapolation from a concentration that causes escape impairing effects in animals, animal to human 

24 differences and human variability, resulting in an IDLH value of 6,700 ppm. This value is supported by the 

25 human data [Patty and Yant 1929], which indicated drowsiness following exposure to 10,000 ppm for 10 minutes, 

26 although there were uncertainties with the study. The IDLH value is a health-based value and may not protect 

27 from physical hazards associated with butane exposure. For example, safety concerns may result when butane 

28 exposures exceed 1,400 ppm, which is 10% of the LEL. 

29 
External Review Draft 

March 2015 

8

This information is distributed solely for the purpose of pre-dissemination peer review under applicable 

information quality guidelines. It has not been formally disseminated by the National Institute for Occupational 

Safety and Health. It does not represent and should not be construed to represent any agency determination or 

policy. 

1 5.0 References 

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9 AIHA (American Industrial Hygiene Association) [2010]. Emergency response planning guidelines (ERPG) and 

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13 AIHA (American Industrial Hygiene Association) [1989]. Odor thresholds for chemicals with established 

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External Review Draft 

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information quality guidelines. It has not been formally disseminated by the National Institute for Occupational 

Safety and Health. It does not represent and should not be construed to represent any agency determination or 

policy. 

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45 Zakhari S [1977]. Butane. In: Goldberg L, ed. Non-fluorinated propellants and solvents for aerosols. Cleveland, 

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