Determination of Methylene Chloride in Indoor Air

Methylene chloride has long been used in industry, academia and has been one of the primary extraction solvents for environmental applications. In recent years, the US EPA has issued several risk assessments and regulations regarding the use of methylene chloride.

In March 2019, the EPA regulated sales of methylene chloride in paint and coating removers for consumer use. In November 2022, the EPA released a final revised risk determination for methylene chloride, which found that it presented an unreasonable risk of injury to health. In April 2024, the US EPA finalized a rule that prohibits nearly all uses of methylene chloride, with some exceptions.

For those who continue to use methylene chloride, a workplace chemical protection plan may be required, which includes baseline air monitoring.

The current Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) for methylene chloride is 25 ppmV. The average exposure to methylene chloride over an eight-hour period should not exceed 25 ppmV. The short-term exposure limit (STEL) is 125 ppmV over any 15-minute period.

This document outlines methodology for determination of methylene chloride in air using active air sampling with analysis by thermal desorption GC-MS. The GERSTEL Internal Standard/Dry Purge module is a station that attaches to the MPS rail and is used for automated spiking of internal standards. The ISDP can also be used to dry purge sorbent tubes where excess water or solvent may adversely affect the trapping and transfer of analytes from the adsorbent tube to the GC column.