Chemical Use and Hazard Management Continued

1. Chemical Use and Hazard Management Continued Session 6 Laboratory Safety Training

2. Compressed Gases • Average cylinder weighs 140 lbs and has 3000 psi of pressure. • Dot code stamp on neck and last test date, steel every 10 years. • Spot checks of cylinders reveal 10% were significantly beyond the test date. • Call the distributor whenever you find them and have them supply new ones.

3. Compressed Gases Cont. • Types of gas in each cylinder must be properly labeled, color codes are unreliable do not use them! • Store similar types together, separate flammable from oxidizers by at least 25 ft or a fire wall at least 5ft high with a 30 minute rating.

4. Compressed Gases Cont. • Empties should be separate from full cylinders and the area should be labeled. • Cylinders should never be stored or used in any way that: • blocks a means of egress • inhibits flow to a fume hood • where they could be struck by moving equipment

5. Compressed Gases Cont. • Always store cylinders in an upright position. • Cylinders should be transported by using a hand truck where it is strapped in well • Never move by rolling them!! • Caps must be in place when moving

6. Compressed Gases Cont. • Cylinders must always be secure in the lab with an adjustable chain or strap with no slack, free standing units work well where there is no surface to secure to. • Use valves appropriate to the gas, Never lubricate valves. Never use homemade adaptors or modify valves unless you have the manufacturers approval. • Never used compressed gas to blow dust or dirt.

7. Compressed Gases Cont. • Understand a sudden release of compressed gas can cause an unsecured gas hose to whip dangerously causing static charges that could ignite a flammable gas. • Always turn the gas off first before extinguishing a flame. • Never bleed cylinders empty.

8. Compressed Gases Cont. • Do not put oil or grease on the high-pressure side of an oxidizing gas (O2, Cl ) or an explosion could occur. • Always use the correct type of tubing for the gas and ensure it is sound, e.g. do not use copper with acetylene, explosive acetylides could form. Flash arrestors should also be used with acetylene.

9. Compressed Gases Cont. • Toxic gas should always be used in a fume hood or ventilated cabinet and check for leaks using soap solutions. • Safety glasses must always be worn when working with compressed gases. • If your cylinder is leaking and you can not stop it open a window (if possible) turn off all reactions and get out.

10. Cryogens • A liquefied gas is a gas that is less than 73.3 C (-100 F). • Most common are Ar O, He, N, H, CH4. • Most have a very high expansion ratio and can cause asphyxiation if this occurs in poorly ventilated or small rooms. • Flammability can be a problem.

11. Cryogens Cont. • Liquid He, and N can, under the right conditions, condense Oxygen from the air causing oxygen enrichment (fire hazard). • Burns to the skin can result from direct contact with a cryogen, un-insulated piping, or equipment containing a cryogen. • Permanent damage can occur if liquid cryogen gets into the eye.

12. Cryogens Cont. • The properties of some materials change drastically at very cold temperatures: ductile materials can become brittle, material shrinkage can exceed anticipated values, and leaks can develop that are undetectable even under pressure. • Storage must be in an insulated dewar flask of glass or metal. Try to avoid exposed portions of glass, if so, tape to prevent injury if it explodes (unless it is an oxidizer). A loose fitting lid should be on to allow for escaping gas and to prevent air or moisture from getting in.

13. Cryogens Cont. • When there is the possibility of contact with a cryogen always wear full face shields aprons, gloves or mitts. • Helium and hydrogen can solidify atmospheric air. If air is not excluded from systems containing these cryogens, vents or exhaust ports to the atmosphere (relied upon for pressure relief) may become plugged by solidified air and lead to system overpressure and vessel failure. Also, if air condenses between the exterior metal surface of the system and the insulating layer, when it warms and vaporizes it can rip off the insulation with explosive force.

14. Cryogens Cont. • Liquid cryogens warmed above critical temperatures will generate high pressures. This can cause a confining vessel to rupture or even explode. For example, small containers such as stoppered test tubes have over-pressurized and produced flying fragments. Fully containing a cryogenic fluid as a liquid at room temperature is usually not feasible-e.g., the pressure required to maintain liquid nitrogen at room temperature is 43,000 psi.

15. Cryogens Cont. • Cryogens can create oxygen deficiency because they have large liquid-to-gas expansion ratios (generally >700). A small liquid spill produces a large volume of gas that can displace the air in a confined space, thus creating a serious oxygen deficiency that can suffocate occupants of the area. • Some cryogens are chemically very reactive (e.g., O2); others are flammable (e.g., H2 and CH4).

16. Cryogens Cont. • Cryogenic fluids with a boiling point below that of liquid oxygen may condense oxygen from the air if exposed to the atmosphere. • Because oxygen does not evaporate as rapidly as liquid nitrogen, it will accumulate and may cause violent reactions with incompatible materials in the system

17. Ionizing Radiation • Three types of radiation emitted from various isotopes • Alpha charged particles containing 2 protons, 2 neutrons. • Can be emitted by from certain heavy atoms such as uranium and thorium. Move in straight lines, slowly. Can be stopped by a piece of paper or by skin, but if inhaled or gets into an open wound can very damaging inside the body.

18. Ionizing Radiation • ß - Beta particles electrons emitted with very high energy from many radioisotopes. • Positively charged counterparts of beta particles are called positrons and can be shielded by thin metal foils or ¼ inch plastic. • Examples are tritium, phosphorus-32, and carbon-14. • can be stopped by the skin • can cause serious damage to the eyes and to the skin.

19. Ionizing Radiation Cont. • Gamma rays and x-rays , extremely energetic photons, have no mass or charge. • Gamma rays are emitted from the nucleus during decay,and can be produced by particle accelerators, and nuclear reactors. X-rays are are emitted from the electron shells. • Extremely dense materials, such as lead or depleted uranium are needed to shield these particles. • Neutrons – Uncharged particles, emitted from the nucleus during decay. Can be shielded by water paraffin, boron, and concrete.

20. Ionizing Radiation Cont. • The Threshold Limit Values (TLVs) published by the ACGIH (American Conference of Governmental Industrial Hygienists) are used in many jurisdictions occupational exposure limits or guidelines: • 20 mSv - TLV for average annual dose for radiation workers, averaged over five years • 1 mSv - Recommended annual dose limit for general public (ICRP - International Commission on Radiological Protection).

21. Ionizing Radiation Cont. • TlV’s Continued: • 1rem = 20 mSv, 1 S=100rem. • Half life , 125 I - 60 days, 131 I – 8 days activity is reduced by half.

22. Ionizing Radiation Cont. • The average lifetime risk of death from cancer following an acute dose equivalent to all body organs of 0.1 Sv (10 rem) is estimated to be 0.8% • This increase in lifetime risk is about 4% of the current baseline risk of death due to cancer in the United States. The current baseline risk of cancer induction in the United States is approximately 25%.  Another way of stating this risk: • A dose of 10 mrem creates a risk of death from cancer of approximately 1 in 1,000,000.

23. Ionizing Radiation Cont. • Damage occurs to the body through interaction with a part of the cell or indirectly by the formation of free radicals and ultimately changes within the DNA of the cell. • The amount of damage depends on many factors including the dose rate, the size of the dose, the site of exposure.

24. Ionizing Radiation Cont. • Effects may be short or long term, acute short term effects = 100,000 mrads (100 rad) in less than 1 week will cause nausea, diarrhea, fatigue, hair loss, sterility and easy bruising. Over 600 rads is fatal. Long term low exposures can lead to cancer. • No completely safe limit of exposure is known which is why we try to reduce exposures to ALARA (as low as reasonably achievable) levels.

25. Lasers • Class 1 - Not able to cause biological injury, exempt from any controls. • A Class 1 laser is considered safe based upon current medical knowledge. • This class includes all lasers or laser systems which cannot emit levels of optical radiation above the exposure limits for the eye under any exposure conditions inherent in the design of the laser product. • There may be a more hazardous laser embedded in the enclosure of a Class 1 product, but no harmful radiation can escape the enclosure.

26. Lasers Cont. • Class 2a & 2b- Ocular hazard only if viewed for more than the blink response (0.25 seconds). All wavelengths are of the visible (0.4-0.7m m) portion of the electromagnetic spectrum and less than 1mW of power. A Class 2 laser or laser system must emit a visible laser beam. Because of its brightness, Class 2 laser light will be too dazzling to stare into for extended periods. Momentary viewing is not considered hazardous since the upper radiant power limit on this type of device is less than the MPE (Maximum Permissible Exposure) for momentary exposure of 0.25 second or less. Intentional extended viewing, however, is considered hazardous.

27. Lasers Cont. • Class 3 laser or laser system can emit any wavelength, but it cannot produce a diffuse (not mirror-like) reflection hazard unless focused or viewed for extended periods at close range. • It is also not considered a fire hazard or serious skin hazard. • Any continuous wave (CW) laser that is not Class 1 or Class 2 is a Class 3 device if its output power is 0.5 W or less. • Since the output beam of such a laser is definitely hazardous for intra-beam viewing, control measures center on eliminating this possibility

28. Lasers Cont. • Class 3a- Ocular and skin hazard for direct exposures. Beams may include wavelengths of visible, infrared or ultraviolet ranges. CW’s maximum power between 1mW and 5mW. Pulsed radiant energy cannot exceed 0.125J with exposure time <0.25s. • Class 3b- Beams may include wavelengths of visible, infrared, or ultraviolet ranges. Emit no more than 5mW-500mW (or 5W) of CW power or 10 J/cm2 of Pulsed power. Acute hazard to eyes and skin from direct beam. Diffuse reflections may be a hazard.

29. Lasers Cont. • Class 4 laser or laser system is any that exceeds the output limits (Accessible Emission Limits, AEL's) of a Class 3 device. • As would be expected, these lasers may be either a fire or skin hazard or a diffuse reflection hazard. Very stringent control measures are required for a Class 4 laser or laser system. • Class 4- Ocular and skin hazard to the direct beam and the diffuse reflections. Beams may include wavelengths of visible, ultraviolet or infrared ranges. CW power greater than 5W, or pulsed radiant energy greater than 10J/cm2. Possible ignition/fire hazard.

30. Lasers Cont. • Some general safety tips/measures for Class 3B and Class 4 lasers include: • Provide key switch interlock systems to prevent unauthorized use. • Wear laser goggles that match the wavelength of the laser system being used. • Prevent reflection of beams - be aware of windows, smooth surfaces and mirrors, watches, etc. in your lab. • Prevent scattered light emissions with beam stops.

31. Lasers Cont. • Never align the beam with unprotected eyes. • Never intentionally stare into any laser beam. • The most important safety measure you can include in your lab is the proper selection of eyewear. Always double check with the manufacturer for their suggested eyewear requirements. Look for the wavelengths and Optical Density(OD) values stamped on the side of the eyewear, does it match the wavelengths of the equipment you are using? 

32. Lasers Cont. • Analysis of laser accident data involving 272 accidents reported to Rockwell Laser Industries from 1964 to 1994 reveals that • eye injury was the most commonly reported laser related accident • eye injury was involved in slightly over 74% of all of the accidents recorded • over 90% of the eye injury cases recorded some functional loss, of which 77% was permanent

33. Lasers Cont. • The most common cause of accidents was accidental eye exposure during beam alignment • The second most common cause of laser accidents resulted from misaligned optics • The third most common cause of accidents was failure to wear available eye protection.

34. Lasers Cont. • Statistical data gathered by LIA concludes that the most common laser incidents are caused by Nd:Yag (29.7%) and Argon (20.5%) lasers. • More importantly are the occupations which are involved. • Out of 12 categories, scientists are involved in 17.6% of laser incidents, second only to technicians (21.3%). • Doctors and Nurses include 9.2% of all incidents, 5th highest of all categories.

35. Lasers Cont. • What are the causes? • Unanticipated eye exposure during improper alignment procedures. • Available eye protection is not often used. • Improper methods of handling high voltage lead to severe shock and even death.

36. Lasers Cont. • Protection for non-beam hazards is often lacking. • Improper restoration of equipment following service. • Incorrect eyewear selection and/or eyewear failure. • Equipment malfunction.

37. Lasers Cont. • It only takes 0.25 seconds(time required for the blink response) with a direct hit from a high powered laser to damage your eyesight. • Don’t become a statistic, protect your eyes