Solvents:
A solvent is a chemical substance which dissolves another substance. The most common solvent is water. Most of the other solvents are called organic solvents. An organic solvent is one which contains the element carbon. You will not be expected to know the chemical formulas for solvents since they tend to be very long and complicated. For example the formula for Xylene is CHCHCH.

Solvents are used extensively in the electronics industry. Compounds such as Isopropyl Alcohol (IPA) and acetone are used to clean and dry wafers, glassware, equipment, and most working surfaces in the lab. In addition, solvents are the principle components of many process chemicals such as photoresist.

Hazards:
There is no such thing as a “safe” solvent. Although some solvents are less hazardous than others, there is a potential hazard associated with every solvent due to its very nature. For example, a solvent that is generally “non-hazardous” during normal use may become very dangerous if a large spill occurs, if there is improper ventilation, or if a leak goes undetected. ALL solvents must be treated with respect. Different people have different tolerances to different solvents. What may not affect one person could be devastating to another.

There are three primary hazards associated with solvents. Many solvents are extremely flammable and present a fire and explosion hazard. Solvents can also be toxic. The principle routes of exposure are inhalation of vapors, skin contact and or ingestion of liquids. Finally, solvents can react violently with acids, resulting in fires or explosions.

Flammability:
A flammable solvent is an organic liquid whose vapor can form an ignitable mixture with air. ALL flammable solvents evaporate readily. ALL the elements of the fire triangle are present when an ignition source is added. Sources of ignition include, but are not limited to, open flames, heaters, electrical equipment, and static electricity. ALL equipment that uses electricity or has moving parts should be considered a possible ignition source.

One measure of the flammability of a solvent is determined by its flash point. The flash point is the lowest temperature at which enough of the solvent can evaporate to form a mixture of vapor and air which will ignite if an ignition source is introduced. Many solvents have flash points below room temperature and are considered to be extremely flammable. For example, the flash point of IPA is 53°F. If a beaker of IPA is allowed to sit uncovered in the middle of a room, enough vapors would escape to form an ignitable mixture. Since room temperature is 72°F or above it would only take one spark to cause a fire or explosion.

The hazards of fire or explosion can be controlled by keeping flammable liquids in closed containers, removing sources of ignition, and providing ventilation to prevent the build-up of vapors.

Storage:
Solvents are stored in the “flammable” storage cabinets provided for that purpose. A small amount (what you will use in a 24 hour period) can be left out of the cabinet if it is kept in a ventilated hood where the vapors will be exhausted away. This will prevent a dangerous build-up of vapors from occurring. Do not leave empty bottles lying around because they will have residual solvents and vapors in them and will become an explosion hazard. Do not store dissimilar chemicals in the same storage cabinets. The vapors from these chemicals could mix and set off a reaction with devastating results. If you are unsure about how to store a chemical, please ask, do not guess.

The “flammable” storage cabinets must be kept away from ignition sources and combustible materials such as boxes, rags, and towels. The cabinets should be located in areas 80°F or lower.

Solvents must be stored and used below eye level in order to reduce the chances of getting solvents in the eyes.

Squeeze bottles should be placed away from sources of ignition and where they will not be subjected to rough handling or sudden shocks. Solvent squeeze bottles must be filled at the hood where the fumes will be exhausted away.

Beakers need to be covered when not in use. Solvents should only be kept in beakers for short periods of time. Beakers of solvent must be filled and used at the solvent bench so the vapors will be exhausted out of the lab area. When you are finished with the solvent, pour the used or contaminated solvent into the proper waste container. This is also done at a chemical hood.

Safety:
The following protective equipment is required to pour solvents and carry bottled solvents:

A. Wrap-around safety glasses
B. Solvent resistant gloves. These should be changed out on a regular basis as needed
C. Lab apron, solvent resistant suit, or acid smock
D. Closed-toe, closed-heel, nonporous shoes

Note: You should use different gloves for working with acids and solvents so you don’t run the risk of mixing chemicals. You should also observe the gloves as they come in contact with solvents to make sure the materials do not breakdown. This would cause holes to form and allow the solvent to come in contact with your skin.