TRIMETHYLBENZENE, MIXED ISOMERS | Occupational Safety and Health Administration

TRIMETHYLBENZENE, MIXED ISOMERS†

Chemical Identification
CAS #	25551-13-7
Formula	C₉H₁₂
Synonyms	[isomers: 1,2,3-trimethylbenzene; 1,2,4-trimethylbenzene; 1,3,5-trimethylbenzene]; hemimellitene; pseudocumene; mesitylene; methylxylene

Physical Properties
Physical description	Clear, colorless liquid with a distinctive, aromatic odor.
Boiling point	329-349°F	Molecular weight	120.2
Freezing point/melting point	-77 - (-)14°F	Vapor pressure	varies
Flash point	112-122°F	Vapor density
Specific gravity	0.86-0.89	Ionization potential	8.27-8.48 eV
Lower explosive limit (LEL)		Upper explosive limit (UEL)
NFPA health rating		NFPA fire rating
NFPA reactivity rating		NFPA special instruction
Vapor hazard ratio (VHR)
Historical exceedance percentage
Target organs

Monitoring Methods Used by OSHA
Analyte code (IMIS no.)	2505	2505
Sampling group	OVSG-1
Sampler/Sampling media	CSC tube (100/50 mg) [SKC 226-01]	SKC 575-002 Passive Sampler [SKC 575-002]
Sampling time^*	240 min	240 min
Sampling volume (TWA)^*	12 L
Sampling flow rate (TWA)^*	0.05 L/min
Sampling volume (STEL/Peak/C)^*
Sampling flow rate (STEL/Peak/C)^*
Analytical method instruments	GC-FID	GC-FID
Method reference	OSHA 5000 (fully validated)	OSHA 1020 (fully validated)
Notes		To obtain sampling and analytical error similar to that available with active sampling, knowledge of the atmospheric pressure and temperature are required, and these should be obtained using NIST-traceable devices. If that is not possible, temperature is assumed to be 22.2 °C, and the atmospheric pressure is estimated based on the elevation of the sampling location. When estimates are used in place of traceable measurements the sampling and analytical error associated with passive sampling is substantially increased, and this makes it more difficult to demonstrate overexposures after considering the 95% lower confidence limit.
Special requirements

^* All sampling instructions above are recommended guidelines for OSHA Compliance Safety and Health Officers (CSHOs), please see the corresponding OSHA method reference for complete details.

Bulk/Wipe Method
Wipe Sampler/Sampling media
Bulk Method

On-Site Screening Techniques
Device
Model/Type
Sampling information (see manufacturer instructions)

**Exposure Limits**
OSHA PEL 8-hour TWA (ST) STEL (C) Ceiling Peak		NIOSH REL Up to 10-hour TWA (ST) STEL (C) Ceiling		ACGIH TLV© 8-hour TWA (ST) STEL (C) Ceiling		CAL/OSHA PEL 8-hour TWA (ST) STEL (C) Ceiling Peak
PEL-TWA	25 ppm (120 mg/m³) Construction and Maritime Industries ONLY	REL-TWA	25 ppm (125 mg/m³)	TLV-TWA	10 ppm [2021]	PEL-TWA	25 ppm (125 mg/m³)
PEL-STEL		REL-STEL		TLV-STEL		PEL-STEL
PEL-C		REL-C		TLV-C		PEL-C
Skin notation	N	Skin notation	N	Skin notation	N	Skin notation	NA
Notes: See 29 CFR 1926.55 Table 1 and 29 CFR 1915.1000 Table Z-Shipyards.		Notes:		Notes:		Notes:
Health factors: See NIH-NLM PubChem.		IDLH
Carcinogenic classifications: TLV-A4 for 1,2,4-trimethylbenzene		Notes:
AIHA emergency response planning guidelines - ERPG-1/ERPG-2/ERPG-3:

Additional Resources and Literature References

NOAA: CAMEO Chemicals - 1,3,5-Trimethylbenzene

NIOSH: Pocket Guide to Chemical Hazards - 1,2,3-Trimethylbenzene

Literature References

NOAA: CAMEO Chemicals - 1,2,4-Trimethylbenzene.
1,2,4-Trimethylbenzene, 1,3,5-Trimethylbenzene.
ACGIH: Threshold Limit Values (TLVs) and Biological Exposure Indices (BEIs) - Trimethyl benzene (mixed isomers). See annual publication for most recent information.
Järnberg, J., Ståhlbom, B., Johanson, G. and Löf, A.: Urinary excretion of dimethylhippuric acids in humans after exposure to trimethylbenzenes. Int. Arch. Occup. Environ. Health 69(6): 491-497, 1997.
Jones, K., Meldrum, M., Baird, E., Cottrell, S., Kaur, P., Plant, N., Dyne, D., Cocker, J.: Biological monitoring for trimethylbenzene exposure - a human volunteer study and a practical example in the workplace. The Annals of Occupational Hygiene. 50 (6): 593-598, 2006.
NIOSH: Recommendations for Occupational Safety and Health - Compendium of Policy Documents and Statements. January 1992.
NIOSH/CEC/IPCS: International Chemical Safety Cards - Trimethyl Benzene (Mixed Isomers). June 3, 2002.

Last Updated Date : 05/12/2022

Group Sampling Information
Sampling Media	Sampling Time (If there are exceptions they will be in Notes)	TWA Sampling Volume (If there are exceptions they will be in Notes)	TWA Flow Rate (If there are exceptions they will be in Notes)
CSC Tube (100/50 mg sections, 20/40 mesh), [SKC 226-01]	240 min	12 L	0.05 L/min

Analytes Sampling Information
Analytes	IMIS Code	Wipe Sampling
Isobutyl Acetate	1534	No
n-Butyl Acetate	0440	No
sec-Butyl Acetate	0441	No
tert-Butyl Acetate	0442	No
Toluene**	2460	No
Ethyl Benzene	1080	No
Perchloroethylene (Tetrachloroethylene)**	2020	No
Trichloroethylene**	2490	No
Xylene	2590	No
Trimethylbenzene	2505	No
Benzene***	0320	No
Ethyl Acetate****	1040	No
n-Propyl Acetate‡	2180	No
Pentane‡‡	1990	No
Cyclohexane‡‡‡	0810	No
Heptane*	1371	No
n-Hexane‡‡‡‡	1380	No
Nonane*	N807	No
Octane*	1957	No

Notes

Request any (up to three (3)) of these analytes together.

Alternatively request IMIS Code Q115 and SLTC will report any significant amounts of these analytes.

Results for unrequested analytes in this group will be reported if significant amount are found.

Toluene, sec-Butyl Acetate, Benzene and Isobutyl Alcohol all have/are known interferences. Please indicate on the 91A which of these compounds are known to be present.

There is no need to contact SLTC before sampling.

*80 min (4L)

**Peak sampling 1 min (0.05 L) and Ceiling sampling 5 min (0.25 L)

***STEL sampling 15 min (0.75 L)

****120 min (6 L)

‡200 min (10 L)

‡‡45 min (2.25 L)

‡‡‡190 min (9.5 L)

‡‡‡‡98 min (4.9 L)

TRIMETHYLBENZENE, MIXED ISOMERS†

Chemical Identification

Physical Properties

Monitoring Methods Used by OSHA

Bulk/Wipe Method

On-Site Screening Techniques

Exposure Limits

Additional Resources and Literature References