Reducing Hazardous Exposure to Organic Solvents

According to the Occupational Safety & Health Administration (OSHA), the “health hazards associated with solvent exposure include toxicity to the nervous system, reproductive damage, liver and kidney damage, respiratory impairment, cancer, and dermatitis.” [1] 

What is a Solvent?

A Solvent is any substance (solid, liquid, or gas) that can dissolve another solid, liquid, or gas (called a solute) to form a solution. A solution is more than a mixture of two different substances because the solvent and solute will have chemical interactions that link them together based on their respective chemical properties. Whereas the individual components of a mixture can be separated by means of mechanical filtration, solvents cannot. When referred to in industrial applications, a solvent is usually a liquid Organic Solvent. Organic solvents are carbon-based and used to dissolve solids, liquids and gases. There are many strong organic solvents that will dissolve (or “attack”) many solid materials, including unwanted residues making them useful in a variety of applications such as:

• in paints, inks, varnishes, lacquers and other coatings
• as cleaners and degreasers
• in paint strippers
• in glues, adhesives and spray products
• as refrigerants and coolants
• in dry cleaning
• in nail polish removers
• in detergents
• numerous other places at work and at home [2]

Common solvents include:

• Acetone
• Toluene
• Benzene
• Ethyl Acetate
• Ethanol
• Methanol
• Xylene
• MEK (Methyl Ethyl Ketone)
• Acetic Acid
• Hexane
• Petroleum Ether
• Methylene Chloride

It should be noted that care should be taken when using and storing these solvents because of their strong dissolving properties. Some plastic storage bins can and will be attacked and disintegrated by many of organic solvents.

General Solvent Safety

The most important thing to remember about organic solvent safety is that they present a significant flammability hazard. Consequently, great care should be taken during storage and handling of organic solvents, especially large quantities of organic solvents. Storage drums should be well grounded to prevent any spark from igniting the liquid, electrical devices used in areas of high usage should be intrinsically safe, and there should be absolutely no smoking around these chemicals. When “hot work” needs to be done in an area of high solvent use, permits must be obtained and the area must be cleared of all solvents and ventilated before work can begin. Furthermore, there should be engineering controls in place to ventilate storage areas and places of high usage in case of spills that would produce extremely flammable mixtures in the air.

Furthermore, besides the flammability considerations, there are other accepted workplace practices that should be implemented when dealing with organic solvents. The California Department of Health Services and the California Department of Industrial Relations (HESIS) recommend basic safe work procedures to avoid overexposure to solvents. Some of these include:

• Don’t wash your hands with solvent.
• Use proper personal protection equipment (ppe) when working with solvents. This will keep solvents off your skin and clothes- if clothes do get wet with solvent; change clothes right away.
• Use the minimal amount of solvent necessary for your application.
• Cover or seal solvent-filled containers when they are not in use. Also contain solvent-soaked items, like used rags.
• Keep areas properly ventilated: make sure fans and exhaust systems are turned on when solvents are used.
• Storage- Always label organic solvent containers.
• Never enter a confined space with the proper PPE and respiratory equipment that are (or could potentially be) contaminated with solvents.
• Label and store solvent waste appropriately. [2]

Respiratory Solvent Safety

Inhalation of solvent vapors and mists is one of the most common ways of being overexposed to solvents. Vapors form as solvents evaporate. Additionally, mist can be inhaled during solvent spraying applications. When these mist and vapors are inhaled, they are absorbed into the bloodstream through the lungs.

The Material Safety Data Sheets (MSDS) of solvents should always be referenced prior to handling and using the chemical. Let’s use Acetone as example:

Acetone is a commonly used solvent. Under “Potential Health Effects” by Inhalation, the MSDS notes that “Inhalation of vapors irritates the respiratory tract. May cause coughing, dizziness, dullness, and headache. Higher concentrations can produce central nervous system depression, narcosis, and unconsciousness.” [3]

Although chemical composition varies from solvent to solvent, it is important to consider respiratory safety engineering controls for all solvent use.

What to Consider When Choosing a Ventilation System

Regarding ventilation as a safety engineering control, HESIS explains that “fans are most effective when they remove vapors at the source, by pulling the air away from the work.” For instance, a fan or fume extraction device that is placed at the opposite end of the room from the chemical and operator will do very little to prevent the operator from inhaling fumes, especially if it is a large quantity. As an additional example, placing an overhead hood over an operator working with solvents would do little to minimize his/her exposure as the air would be pulled right through the breathing zone.

Source-capture fume extractors (or local exhaust ventilation) come in a variety of configurations. Depending on a variety of factors, one model may work better for one person over another. There are several variables that should be considered when choosing an appropriate ventilation system for your operation.

Quantity- The amount of solvent that is being used is one of the most important factors in deciding on a ventilation system. For instance, for someone that utilizes large amounts of solvent, an Exterior-Ducting Exhaust Hood may be used. Most organic vapor filter cartridges only absorb a fraction of their weight, so a 10lb filter could absorb at most 4lbs of vapor. For high use applications, this amount of vapor could be reached after a day’s use. Consequently, using a ducted exhaust hood where the vapors could be vented to either a large scrubber, incinerator, or the outside would be optimal. Small amounts of solvent may require less air volume to remove. For those that use smaller amounts of solvent, ventilation options like the Winged Sentry with Lid (this benchtop unit has infinitely adjustable side “wing flaps” for operator control) and Portable Floor Sentry exist (this unit sits on the floor and reaches benchtops via self-supportive flex hose). These two units are equipped with activated carbon filtration.

A 30″ Wide Ducted Exhaust Hood is pictured above.
The Model 200 Winged Sentry with Lid is pictured above.
The Model 300 Portable Floor Sentry is pictured above.

Type- Equally as important as the quantity of the solvent is the type of solvent. Since we are discussing organic solvents then an organic vapor cartridge (such as activated carbon) would nearly always be appropriate. The exceptions are very light molecular weight solvents such as methylene chloride, methanol, formaldehyde, ethyl ether, and even ethanol to an extent. Whereas treated organic vapor filters exist for formaldehyde and other light aldehydes, none such specialized filters exist for other light solvents. Therefore, ductless hoods (with filtration media) would not be appropriate for these types of solvents. 

A Certified Industrial Hygienist or Safety Engineer should be consulted when developing a ventilation system for solvent control. For information on individual products that can be used for these systems (including the ones mentioned above), please call Sentry Air Systems at 1.800.799.4609, email us at sales@sentryair.com, or fill out this form to receive more information.

References

[1] OSHA. Safety & Health Topics: Solvents. <http://www.osha.gov/SLTC/solvents/index.html>
[3] J.T. Baker. MSDS for Acetone. <http://www.jtbaker.com/msds/englishhtml/a0446.htm>