Chemical air filtration system aids in reducing exposure to methylene chloride vapor

stripping-paintEarlier this month, a New Jersey cabinet manufacturer was cited by OSHA for 15 safety and health violations; seven were serious violations for exposing employees to unsafe levels of methylene chloride vapor.

In their report, OSHA proposed a penalty of $32,340 for just those seven serious violations – ouch!

A serious violation occurs when there is substantial probability that death or serious physical harm could result from a hazard about which the employer knew or should have known.

So what is methylene chloride?

According to OSHA, Methylene Chloride (or Dichloromethane), is a volatile, colorless liquid with a chloroform-like odor.

While its use as an adhesive and paint stripper are most common, it is also used in:

  • Cleaners and degreasers
  • Residual solvent in pharmaceutical manufacturing
  • Polyurethane foam production
  • Polycarbonate resin production
  • Aids in the decaffeination of coffee and teas

Why is it so serious?

The Agency for Toxic Substances & Disease Registry (ATSDR) lists the side effects for both acute and chronic exposure. A summation of their list can be found in the chart below.

Side effects of methylene chloride vapor

Acute Exposure

Chronic Exposure

Central nervous system depression, headache, drowsiness, slurred speech, decreased alertness, slowed reaction times, irritability, impaired gait, rapid loss of consciousness, coma, seizures, elevated carbon monoxide levels in the blood, inflammation of the lungs, accumulation of fluids in the lungs

Reasonably anticipated human carcinogen.

In order to protect workers from over exposure, the following limits are in place:




Occupational Safety and Health Administration (OSHA)

Permissible Exposure Limit (PEL)

25 ppm TWA

Short Term Exposure Limit (STEL)

125 ppm

Action Level

12.5 ppm TWA

American Conference of Industrial Hygienists (ACGIH)

Threshold Limit Value

50 ppm TWA

Methylene Chloride odor thresholdIn their Medical Management Guidelines for Methylene Chloride, ATSDR says that inhalation is the most important route of exposure as methylene chloride vapor is readily absorbed from the lungs.

They further explain that odor is not an adequate warning property for methylene chloride, because the odor threshold is 250 ppm – 10 times higher than OSHA’s PEL of 25 ppm.

Simply put – if you can smell methylene chloride, you are over exposed.

What are my responsibilities as an employer?

According to OSHA’s General Duty Clause:

  • Employers shall furnish to each of his employees employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to his employees;
  • Shall comply with occupational safety and health standards promulgated under this Act.

For employers to adhere to the exposure limits, personnel monitoring must be done. The below chart provided by OSHA describes required air sampling monitoring activities based on the action level.

Table 1: Monitoring Requirements

Exposure Scenario

Required Monitoring Activity

Below the action level (12.5 ppm) and at or below the STEL (125 ppm)

No eight-hour TWA or STEL monitoring required

Below the action level (12.5 ppm) and above the STEL (125 ppm)

No eight-hour TWA monitoring required; monitor STEL exposures every three months.

At or above the action level (12.5 ppm), at or below the PEL (25 ppm TWA), and at or below the STEL (125 ppm)

Monitor eight-hour TWA exposures every six months

At or above the action level (12.5 ppm), at or below the PEL (25 ppm TWA), and above the STEL (125 ppm)

Monitor eight-hour TWA exposures every six months and monitor STEL exposures every three months.

Above the PEL (25 ppm TWA), and at or below the STEL (125 ppm)

Monitor eight-hour exposures every three months.

Above the PEL (25 ppm TWA) and above the STEL (125 ppm)

Monitor eight-hour TWA exposures and STEL exposures every three months.


More information on OSHA’s standard on methylene chloride can be found in Title 29, Parts 1910.1052, 1915.1052, 1926.1152.

What are some ventilation options?

If your workplace intermittently uses methylene chloride-containing materials, we recommend a negative-pressure source-capture engineering safety control system.

A source-capture, negative-pressure system will pull harmful methylene chloride vapor away from the operator’s breathing zone from the point of emission.

At Sentry Air Systems, we specialize in these types of air cleaners and offer a range of product configurations depending on your application.

We also recommend using our activated carbon filters inside these units to adsorb the vapor molecules within the porous structure of the carbon media granules.

A popular option is our Model 300 Winged Sentry with lid (shown below). This portable, benchtop configuration allows easy placement in a room, takes up minimal space and utilizes a powerful fan to pull the vapor into its filter chamber.

Sentry Air Systems SS-300-WSL

Sentry Air Systems SS-300-WSL

Visit our chemical applications page on our website for other available configurations.

Product Tested, Industrial Hygienist Approved.

We had a third party, certified industrial hygienist test our Model 300 Winged Sentry with lid equipped with activated carbon filtration, to determine the unit’s effectiveness at removing methylene chloride vapors produced by the evaporation of a measured amount of liquid methylene chloride.

A summary of the test results is noted in the below chart.


Avg. Flow Rate


Sampling Time


Sample Volume


MC found

 mg (ppm)

% Removal

Winged Sentry inlet




0.84 (81)

Winged Sentry outlet




0.062 (6.2)


Personal sample (operator)




0.069 (6.9)

Area sample




0.056 (5.3)



< 0.003

The entire test report is located on our website under the Data Tab page.The personal sample taken on the operator during the experiment was found to be 6.9 ppm of methylene chloride. Assuming no further exposure to methylene chloride during the day, the 8-hr. TWA would have been 0.43 ppm; significantly below OSHA’s TWA exposure limit of 25 ppm.

Be proactive, not reactive.

When considering the potential fines involved for violating OSHA exposure limits, it becomes clear that employers should consider multiple engineering safety controls to help protect against employee exposure.

While we cannot promise or guarantee zero OSHA citations for methylene chloride exposure, Sentry Air Systems is able to provide air filtration solutions that offer significant respiratory protection at a price substantially lower than potential fines.

Contact Sentry Air

For more information about chemical fume control, contact Sentry Air Systems at 800.799.4609, email, visit our website or fill out the feedback form below.