Things have changed. On April 10 the final phase of the new OSHA standard on methylene chloride became effective. This standard dramatically changes the way in which spot cleaning must be carried out. “Must” is the key word here.
For the uninitiated, methylene chloride (also known as MEC and dichloromethane) is the primary ingredient in most – and I mean most – spot-cleaning fluids. It is used for a very good reason: It works. No other chemical has been found that is as effective as MEC for the removal of plastisol and other textile inks.
MEC had long been a mildly regulated product. An established threshold limit value (TLV) of 500 parts per million meant that even the most careless spot cleaning would not exceed the TLV. Over the past few years, however, there have been concerns about the health and safety implications of products containing MEC. The primary concern has been the possible carcinogenic potential of such products. This is not just limited to spot cleaners, but also to adhesives, both aerosol and bulk, along with any other products that contain MEC.
The new standard sets a mandatory maximum TLV of 25 ppm, with an “action” level of 12.5 ppm. The action level is the point where the employer has the legal responsibility to ensure that their employees’ exposure does not exceed the TLV and that they are being medically supervised to check for any long-term effects of exposure.
Think about it: 25 ppm compared to 500 ppm. That’s quite a reduction in the allowable level! The good news, though, is that in the normal course of a day it is almost impossible to reach an exposure of 500 ppm. Typical levels I have observed in print shops range from 5-35 ppm. You would literally need to hold your head over a bucket of MEC to get close to 500 ppm (just take my word for it!).
All businesses, no matter how few or how many employees they have, must comply with this new standard. Outlined below is a summary of the standard, which is actually 250-plus pages.
Note: Because we’re dealing with government agencies and their terminology, I’m providing phrases and abbreviations you’re likely to come across in dealing with such operations as OSHA. You may want to get out your highlighting marker now.
The MEC you breathe
OSHA’s methylene chloride standard actually took effect in 1997, but has been phased in over the past three years. The final action date of this standard was April 10, so all employers whose facilities have methylene chloride should currently be complying with the standard.
To comply with the standard, the first step is to determine the exposure level of methylene chloride to the employees in the facility. This is done by taking one or more “personal breathing zone” air samples. Monitoring can be accomplished in-house or by an independent testing service.
The simplest method of testing for the amount of MEC that a worker could be inhaling is for employees to wear special badges on their collars for a typical eight-hour shift. These are similar to the radiation monitors worn by X-ray technicians. Once the test is completed, the badges are sent to a lab for analysis.
These badges can be purchased with the analysis prepaid. It is essential to follow the badge manufacturer’s instructions exactly to achieve an accurate test result. One correct monitor type is 3M Co.’s 3520 Organic Vapor/Monitor with backup section.
If the results are 12.5 ppm or below, then no further action on your part is required (other than documentation of the test). If the results are between 12.5 ppm and 25 ppm (the time-weighted average, or TWA) and are within the short-term exposure level (STEL) of 125 ppm, the employer must begin medical surveillance of the exposed employees. Medical surveillance basically means having those employees who may come into contact with MEC in the workplace take a targeted oral and physical medical examination, as outlined by OSHA. If exposure is in excess of the permissible exposure limit (PEL) of 25 ppm and/or the STEL of 125 ppm, then action must be taken within 60 days to comply with the standard.
The complete standard including medical compliance information can be found on OSHA’s website at: www.osha-slc.gov/SLTC/methylenechloride/index.html.
“OK, what other options do I have?” you ask. Spot-cleaning fluids can be separated into three basic types:
1. Non-flammable products based upon methylene chloride (remember, these have been used because they’re highly effective).
2. Flammable solutions. These normally contain a very high content of acetone (sometimes they are 100% acetone). The obvious drawback here is flammability. As a cleaner, acetone does OK; however, you can expect a higher degree of color bleed (ink running into other parts of the garment).
3. The “new kids on the block,” utilizing one of two solvents. One is 141B dichlorofluoroethane, a product developed as a replacement for some of the previously phased-out Freon products. As a cleaner it will remove some plastisol screenprinting inks. It does, however, take more product to accomplish the operation. And it is classified as a Class 2 ozone depleter.
The other solvent being utilized is normal-Propyl Bromide (nPB). This is quite new, with very little data available. It is currently unregulated; however, there seem to be a lot of reports floating around that question the health risk potential of this product, as well as showing it to possibly have up to 100 times the ozone depletion potential of some phased-out Freons. Other disadvantages with these types of products are their costs, which are typically about 50% higher than conventional spot-cleaning fluids, and, more importantly, their questionable ability to do the job!
Is there any magic in the chemical industry that will simply make the stains go away with a wink of the eye? No. Do I have a magic wand that can make water do the job of spot-cleaning solvents? Again, no.
Will there be safer, more effective products available in the future? I am optimistic that the answer is yes. Until then, use the chemical that is right for you, and use the correct procedures and equipment to ensure safe, compliant spot cleaning.[/fourcol_three] [fourcol_one_last]
What else can you do?
The final step to a safe spot-cleaning operation is to look at the equipment being used. At the heart of any spot-cleaning system is the gun. Guns come in various sizes and have different performance characteristics. Which gun is best? The one that does the job for you.
Don’t be misled by claims of 2,000 psi or even 3,000 psi. All spot-cleaning guns have the potential to develop very high pressures when the nozzle is sealed off and a pressure gauge is attached. It doesn’t take a ballistics expert to know that at extreme pressures, the fluid stream would cut through the fabric like Darth Vader’s light saber.
The actual pressure of the fluid stream as it hits the fabric is between 40 psi and 60 psi. And don’t think that this is not enough pressure to puncture your skin, because it most certainly is. Always keep your body away from the fluid stream and never, never point the gun at anyone. Look for a gun that has good balance and an adjustable nozzle. The manufacturer’s warranty will tell you a lot about the quality of the gun.
Almost a necessity now is a cleaning station. Because of the job that it has to do, high airflow is paramount. Airflow is measured in cubic feet per minute (cfm); a flow of 500 cfm is an acceptable level for most shops. If your solvent is flammable (like acetone), you must use an explosion-proof unit.
I like a stainless steel cleaning screen that’s sized so that you can lay the soiled area and surrounding fabric over the vacuum unit. If it is too small an area, the fluid will run into the fabric and take longer to dry, possibly causing ringing or stains. If the cleaning surface is too large, then the fabric will take longer to dry, as the air will be diverted to other parts of the cleaning screen.
You also might look for units that offer complete vapor recovery. Exhausters with over-spray shields greatly help to reduce airborne contamination of the workspace. Some exhausters have integrated, activated charcoal filtration that allows the unit to be vented into an open area inside a facility, allowing installation in large buildings where outside ventilation is not practical. Ask the manufacturer for details. Again, you want the equipment that offers the best protection and does the best job for you.