Handling and Storing Compressed Gases in Cylinders
Compressed gases are unique in that they have the potential to be exposed simultaneously to both mechanical and chemical hazards. If the gas is flammable, fire or explosion is possible under certain conditions. Additional hazards can arise from the toxicity or reactivity of the gas. And since so much potential energy is created through the compression of the gas, a cylinder can be a potential rocket.
Thus, careful procedures are necessary for handling and storing compressed gas cylinders. Here are some tips to reduce their potential hazard.
Cylinder Handling
- always use a cylinder hand truck for transport.
- the cylinder cap should always be firmly in place when the cylinder is moved.
- cylinders should be chained or otherwise secured in an upright position at all times.
- do not drop cylinders or permit them to fall against each other.
- leave valve caps on cylinders until secured and ready for use.
- all valves should be closed when not in use.
- use the proper regulator for the particular gas.
- always consider cylinders to be full and handle accordingly.
- cylinders of non-liquefied gases should be considered empty while a little positive pressure (approx. 25 psig) still remains in order to prevent suck-back and contamination.
- cylinders containing liquefied gases should never be completely emptied in order to prevent suck-back and contamination.
- the contents of cylinders must be identified with decals, stencils, glued or wired-on tags, or other markings on the cylinders. Color codes alone or tags hung around the necks of the cylinders are not acceptable. Cylinders lacking proper identification must not be accepted from vendors.
- employees must not attempt to repair cylinders or cylinder valves or to force stuck or frozen cylinder valves.
- empty cylinders must be marked "EMPTY" or "MT" with grease pencils. Generally, this marking should be on a large piece of adhesive or masking tape stuck on the cylinder rather than on the cylinder itself. However, some cylinders have tags wired to the valve that identify their contents; in this case, the bottom half of this tag may be torn off to indicate an empty cylinder. In all cases, empty cylinders must be easily identified so as not to be confused or stored with full cylinders.
- demurrage charges continue until cylinders are returned to the supplier; therefore, empty cylinders should be returned promptly. Furthermore, very old cylinders can form shock-sensitive peroxides, another reason to return cylinders as soon as they are empty.
Cylinder Storage
- store cylinders in a fire-resistant, cool, dry, and adequately ventilated area.
- the storage area should not contain any sources of ignition.
- storage area temperature should not exceed 100 degrees Fahrenheit.
- the floor should be level and designed to protect cylinders from dampness.
- cylinders should be protected from weather extremes and direct sunlight.
- store gases supporting combustion at least 25 feet from fuel gases, preferably in another storage area.
All researchers should know the characteristics of the gases he or she uses: toxicity, flammability, compatibility with materials and other gases.
The information for the above article was taken from pages 27-28 of the CWRU Chemical Safety Manual. Please look here for further information on the safe use of compressed gas, or call the DOES office at x2907.
Using Flexible Tubing to Supply Natural Gas to Small Appliances
It is often necessary to supply natural gas to a small appliance (i.e. a Bunsen burner or hot plate) by using a length of plastic or rubber tubing to connect the appliance to a source of gas. Some safety measures should be followed when this is done.
- Always use tubing that is the proper type and size for the job.
- Make sure tubing is securely fastened at both ends and not subject to any physical abuse such as cutting, pinching or burning.
- Never turn off the appliance and leave the gas source turned on. The pressure build up could cause the tubing to burst or the connections to come apart which would allow gas to enter the room/work area.
- Inspect the set-up frequently to make sure that the tubing remains in good condition and that the connections are tight.
Chemical Fume Hoods
Chemical fume hoods provide significant protection from exposure to hazardous materials, protecting the worker from environmental contamination and giving the worker a certain amount of protection. While primarily used as a ventilation device, fume hoods can also offer protection by placing a physical barrier between the worker and a chemical reaction done within a hood, especially when the sash is closed. This barrier can offer protection from hazards such as chemical splashes or sprays and fires.
Chemical fume hoods provide ventilation by discharging any noxious or hazardous vapors, fumes, dusts, and microorganisms generated inside the hood. The air enters the hood from the work opening and is exhausted from the room. However, though hoods contain and exhaust materials during an experiment and dusts or vapors escaping from the apparatus being used, they should still be considered back-up safety devices. Furthermore, they should never be used as a means of disposing of chemicals.
Ventilation Safety
The ventilation offered by fume hoods is not always 100% effective, even when manufactured to exhaust all of the air in the hood; certain conditions can affect their capabilities. For the most part, though, they are extremely efficient if certain conditions are adhered to:
- before starting an experiment, make sure the exhaust blower is operating and air is entering the hood, using a tissue to verify that flow exists.
- periodically check to make sure the air flow through the hood has not changed--check the certification date sticker to verify when it was last checked, and contact DOES if the certification has expired.
- never place your face inside the hood.
- avoid blocking baffle exhaust slots in any way.
- be aware of other room ventilation factors that may interfere with your hood operation such as open doors, open windows, blocked exhaust ports, or heating and air conditioning vents.
- avoid cross drafts and disruptive air currents in front of the fume hood. These can occur through repeated insertion and withdrawal of the workers' arms in and from the work chamber, opening and closing the doors to the laboratory, improper placement of materials or equipment within the work chamber, or brisk walking past the hood while it is in use.
- do not store chemicals or waste in the hood. Do not store radioactive waste in a hood unless the chemical mixture it is in is highly volatile.
Each time the fume hood gets tested, the allowable height of the sash is marked by a certification sticker. DO NOT raise the sash above this sticker.
All chemical fume hoods must be tested and certified at least annually. This is done in-house by DOES. If your certification sticker is out of date, or if you don't have one, call us at 368-2907 to be put on a testing list.
Radiation Clean-up
Over the past month, two incidents occurred on campus concerning spills of radioactive material. However, what could have been serious contamination problems in both of these labs were averted. Lab personnel practiced sound engineering controls and knew the proper protocol in case of a spill.
- Sound engineering controls. In one of the incidents, a vial with radioactive material was dropped, its contents spilling. However, bench paper covered the area of the experiment completely and shielding was in place, greatly limiting the chances of contamination spreading.
- Proper personal protective equipment. Additionally important in the above case was the protection of the worker: lab coats and gloves were worn, limiting the chances of contamination getting onto clothes or hands and being spread unknowingly.
- Knowing protocol in case of a spill. In the other incident, an eppendorf tube exploded inside a centrifuge, spreading radioactive material everywhere. Faced with this daunting clean-up, the lab personnel nonetheless knew what to do. Most important was taking steps to ensure that contamination would not spread; everyone was surveyed for possible contamination, including shoes, a vital step in preventing accidental contamination. One worker had an extra pair that she could change into, leaving the highly contaminated ones aside.
In both cases, the area was quarantined and personnel were no longer allowed in the area. Clean-up began with the floor, further reducing the chances of spreading the contamination.
- Calling the Radiation Safety Office immediately. In both cases, the labs called the Radiation Safety Office right away to report the accident and to ask for assistance in the clean-up. It is important to call us when large spills such as these occur since decontamination might be difficult and lengthy. However, any spill, no matter how minor, must be reported to DOES.
If you have any questions about proper procedures in case of a spill, please call us at x2906.
Real-life Radiation Accidents (and what you can do to prevent them)
Recently the Nuclear Regulatory Commission (NRC) sent an urgent notice to licensees concerning two contamination incidents that occurred at biomedical research facilities. In light of the issuance of this memo, we would like to remind researchers of some basic regulatory issues that came up during these incidents.
The two separate incidents involved ingesting hundreds of microcuries of P32. Since the investigation is ongoing, the NRC has asked licensees to examine and re-evaluate several issues. Please review your laboratory procedures concerning these issues:
Security
Ensure that all radioactive material is secure and that licensed material in use is closely supervised. Limited access to restricted areas is required to prevent unauthorized access to licensed material. Since both incidents discussed in the memo could be cases of misuse of material, security and accountability are highly stressed.
Accountability
Each lab is responsible for all radioactive materials in its possession. It is vital that records are accurately kept, especially waste records, so that we can account for all radioactive materials on campus. Samples of record-keeping forms are in the Radiation Safety Manual. Any theft or loss of materials must be immediately reported to the Radiation Safety Office.
Survey Procedures
In both cases, the internal contamination was detected when the researchers conducted routine surveys of their labs and discovered high background readings. Conducting surveys with appropriate calibrated equipment is therefore a crucial step in safe operations. Be sure that you are using the appropriate probe for your survey (depending upon the isotope) and that you use the proper survey procedures.
It is prudent to routinely survey outside designated RAM-usage areas for cross-contamination.
Food and beverage storage
Eating, drinking and smoking are prohibited in all laboratories. Be very careful that food (especially lunches, snacks and beverages) are stored elsewhere.
If you have questions concerning the issues outlined above, please call the Radiation Safety Office to discuss it (x2906). We are happy to address any radiation issues or concerns that may affect your lab.
Take a Good Look at Those Chemical Warning Labels
You have probably looked at hundreds of chemical warning labels since you started working in a lab. You may have seen so many that you no longer notice the label. However, we would like to remind you that those chemical warnings are important to your health and safety.
More than a Name
Chemical warning labels provide important information about the chemicals you use in the lab. While you can get the same information and more from an MSDS, only a warning label can tell you exactly which chemical is inside that particular container. When you transfer a hazardous chemical from one container to another, the label you put on the new container protects others who may use the chemical in the future-including you.
The Key Word
The most important information on the label is the single word that indicates how hazardous the chemical is. "Danger" means it is the most hazardous kind of chemical. "Warning" signifies a somewhat less hazardous chemical. and "Caution" the least. But even chemicals labeled "Caution" can be harmful to your health if you do not follow proper procedures.
Basic Label Information
Labels list basic information, such as the chemical's name, its hazards (such as whether it is toxic or flammable), the manufacturer's or distributor's name, address and phone number, a list of ingredients, and parts of the body that can be affected by the chemical. Other important information may be given, such as:
- Reactivity of the chemical (what causes it to catch fire, explode, or become a dangerous gas)
- Type of fire extinguisher to use in case of fire
- Type of protective clothing and equipment needed
- Procedures for the safe usage, handling, storage and disposal of chemical
- First aid instruction
- What to do if the chemical spills or leaks
Missing or Damaged Labels
The most dangerous chemical is one without a label: never handle a chemical until you know what it is. If a label is missing or damaged so that it cannot be read completely, notify your supervisor. Label any solutions you create in the lab with at least your name and the bottle's contents, even if it is something innocuous like a salt and water solution. The cost of disposing "unknowns" is great because of the often unnecessary precautions that must be taken.
It's a good idea to get in the habit of reading the warning label before you begin working with a potentially hazardous chemical, even if you've worked with the chemical before-the manufacturer may have changed the formula or concentration. The MSDS for that chemical can give you even more information vital to your health and safety-it is your responsibility to read it.