Module 5: Control Measures to Reduce Exposures

1. Module 5: Control Measures to Reduce Exposures

2. Control MeasuresEngineering Controls • Engineering controls are those that mitigate the dangers of accidents through the use of design and separation. They can be placed in three categories: • Substitution • Isolation • Ventilation

3. Control MeasuresEngineering Controls • Substitution includes the use of a less hazardous material, a change in the process equipment used, or a change in the process itself. Care must be taken to ensure that the substitution actually does result in less hazardous conditions.

4. Teaching objectives Does the alternative alter the experiment’s teaching objectives significantly? Raw material needed Quantity and characteristics of the raw materials Waste generated Physical state, quantity and characteristics of the wastes Cost Equipment, chemicals, waste disposal, etc. Ease of implementation How to Perform a Substitution. Develop Evaluation Criteria • It order to select a substitution chemical the teacher must consider a variety of issues. Some of the criteria of concern are listed below.

5. How to Perform a Substitution. Screen Alternatives • Screen the alternatives to eliminate those that are not feasible for the University • Some preliminary information on each alternative will be needed • Screen using an evaluation matrix with the selected criteria • Select favorable alternatives

6. How to Perform a Substitution. Detailed Evaluation of Alternatives • Quantitative/Qualitative Detailed Evaluation • Not needed if only one alternative remains after the initial screening • Used as a fine tuning to determine which of the remaining alternatives might result in the most favorable for pollution prevention • Pilot Testing • Test alternative before its full implementation

7. Example Evaluation Criteria Educational value Safety risks Input materials Waste materials Cost Resources Ease of implementation Others Alternatives For Experiment A 1. Chemical substitution 2. Microscale 3. Scale down 4. Alternatives 1 and 3 For Experiment B 1. Ag identification and recovery using ascorbic acid 2. Alternative method for Ag identification using KI

8. Control MeasuresEngineering Controls • Isolation is a method of limiting exposure to those students and teachers who are working directly with the hazard, often by enclosing them within a containment structure. While isolation will reduce the risk to those outside the isolated area, it should be accompanied by appropriate controls to ensure that those within are not faced with an increased exposure to the hazard.

9. Control MeasuresEngineering Controls • The most common example of isolation is the elimination of anyone from the laboratory other than those who must be there. Additional students in the room not only create additional distractions and opportunities for accidents but are also potential victims should an accident occur.

10. Control MeasuresEngineering Controls Ventilation is most important for the control of airborne hazards. It involves the removal (from the laboratory) of air that contains a hazardous contaminant and its replacement with uncontaminated outside air. There are two types: local exhaust and general dilution. A properly designed local exhaust system can capture a contaminant where it is generated and remove it before it is dispersed into the work environment.

11. Control MeasuresEngineering Controls Local exhaust is accomplished in most laboratories with the use of a fume hood. These devices are critical for the removal of potentially dangerous gases and vapors for the room. General dilution is accomplished thorough the use of Heating Ventilation and Air Conditioning Systems. The more air changes occur in the laboratory the less likely that a dangerous exposure level will occur. Experiments should never be conducted in poorly ventilated spaces.

12. Engineering Controls Fume Hoods Space is always an issue but do not use fume hoods as storage cabinets. A variety of accidents can happen

13. Engineering Controls Fume Hoods • Fume hoods should be checked and certified as functioning properly. A white card should be placed on the fume hood with the certification date. (If a fume hood is operating marginally, a yellow caution sign should be posted on the hood; if the hood fails completely, a red warning sign must be posted.)

14. Engineering Controls Fume Hoods • Many fume hoods have air flow alarms. However, alarms occasionally fail or are deliberately silenced. • One suggestion is taping tissue to the fume hood sash to provide a visual indication of air flow.

15. Engineering Controls Fume Hoods • Some rules of thumb when using fume hoods: • Keep objects at least 6” inside the hood • Larger objects should be up on blocks or feet to allow air flow to travel underneath • Too much air flow is not necessarily a good thing. Eddies can occur which will force the contaminant back on to the user. Call maintenance if you suspect the fume hood is pulling too much air • If your fume hood is loud, it may indicate that mechanical attention is needed. Call maintenance for a hood evaluation.

16. Engineering Controls Fume Hoods Remember -- adequate ventilation is important in any room in which chemicals are used or stored. Inadequate ventilation limits the kinds of activities that can be done and the chemicals used in the laboratory. An adequate ventilation system should change the room air 4-12 times per hour. All air from laboratories should be exhausted outdoors and not re-circulated in the building. The ducts should be situated so that exhausted air does not enter fresh air intakes.

17. Engineering Controls Fume Hoods Lack of odor is not an adequate criteria of good ventilation since many chemicals have no odor at hazardous levels. A knowledge of the hazardous chemicals being used helps reduce risk from exposure. If the presence of hazardous vapors is suspected, monitoring should be done. Emergency auxiliary ventilation should put a negative pressure on the room so air moves into the room and prevents vapors from being re-circulated through the building.

18. Engineering Controls Fume Hoods Chemical storerooms should have ventilation adequate to keep atmospheric levels of chemicals below their hazardous limits (threshold limit value (TLV) or permissible exposure limit (PEL)). As with room ventilation, 4-12 air changes per hour are recommended on a continuous basis to prevent buildup of toxic or hazardous concentrations of vapors. All ventilation systems should be regularly evaluated to ensure they are operating properly.

19. Engineering Controls Fume Hoods Fume hoods are intended to keep flammable gases, toxic vapors, or noxious odors from entering the general room atmosphere. The American Conference of Government Industrial Hygienists (ACGIH) recommends that hoods be used when working with chemicals having a TLV of 50 ppm or less. The concentrations of vapors in the room must be below the TLV listed in the MSDS for the chemical(s) used. Microscale procedures in which smaller quantities of chemicals are used can reduce exposure to hazardous and noxious vapors.

20. Mechanical SystemsVentilation • LOCAL EXHAUST FANS • Use local exhaust fans and fume hoods to prevent air pollutants and moisture from accumulating in, or spreading beyond, the local area or classroom. Local exhaust fans may be used to exhaust entire rooms (for example, bathrooms or locker rooms). Fume hoods are appropriate for activities that generate significant quantities of pollutants in a local area within a room.

21. “Other” Control Measures • Protective Equipment • respirators, goggles, gloves, lab coats • Safety Equipment • spill kits, safety showers, eyewashes, fire extinguishers, first aid kits, explosion-proof refrigerators Laboratory Maintenance and Inspection • Housekeeping, safety audits, chemical storage, container labeling, spills, etc.

22. “Other” Control Measures • Clean and well organized lab and storage areas decrease the numbers of opportunities for accidents. Good housekeeping includes proper cleaning of glassware, orderly arrangement of chemical containers, pre-staged tools and many other measures. Laboratory Maintenance and Inspection • Perhaps one of the least discussed yet most important area of safety management is housekeeping.

23. Other Protective Systems

24. Fire Detection Systems • Fire Alarms and Heat/Smoke Detectors in classrooms and storage areas provide advanced notice of an incipient fire. Ionization and photoelectric detectors have the capability of saving lives and property if they are installed and maintain correctly. Some general recommendations associated with heat and smoke detectors include: • Don’t install them in corners of walls or ceiling. • Don’t paint them. • Don’t install them in air pathways for vents. • Never cover a detector with a plastic bag or other device.

25. Fire Sprinkler Systems • Fire Sprinkler systems are extremely effective tools for the protection of life and property. They have the best safety record of any fire control device according to the National Fire Protection Association. A note here about how they work. • A sprinkler head is a water outlet that is sealed closed with a cap and a fusible device such as a glass crystal or fusible link. They operate at a given ambient temperature and operate one at a time directly of the seat of the fire. They cause significantly less damage than a fire might.

26. Fire Sprinkler Systems • Some simple procedures will ensure that the sprinkler system will work effectively and not cause undue damage. • Never hang anything from a sprinkler head. • Never paint a sprinkler head. • Avoid sprinkler heads when conducting experiments involving high heat. • Do not store anything within 18 inches of the sprinklers. • In the event a sprinkler activates accidentally, evacuate the room (the first water at the end of the pipe is usually filthy and stagnate) and attempt to control flooding.

27. Electrical Systems • Ground fault interrupters are designed to protect from electrical shock by interrupting a household circuit when there is a difference in the currents in the "hot" and neutral wires. Such a difference indicates that an abnormal diversion of current from the "hot" wire is occurring. Such a current might be flowing in the ground wire, such as a leakage current from a motor or from capacitors. More importantly, that current diversion may be occurring because a person has come into contact with the "hot" wire and is being shocked. When a circuit is functioning normally, all the return current from an appliance flows through the neutral wire, so the presence of a difference between "hot" and neutral currents represents a malfunction which in some circumstances could produce a dangerous or even lethal shock hazard.

28. Electrical Systems • GFCIs are sensitive and trip easily. To reset them first ensure that there is no electrical hazard and then simply push the reset button located in the middle of the receptacle. In some cases normal duplex receptacles are wired to one GFCI. If this case you will have to locate the GFCI and reset it. Any failure or a GFCI to reset or if you cannot find it, contact facilities maintenance. • Ground fault interrupters are subject to aging and may need replacing after a number of years. The GFCI ordinarily trips off and cannot be reset using the Reset button. If this occurs, notify facilities maintenance to test and/or replace the GFCI.

29. Electrical Systems To test a GFCI, press the “test” button. The power should shut off. Occasionally GFCIs fail to work as designed (even though pressing the “test” button shuts off the power). To ensure a GFCI is working properly, contact Maintenance for testing.

30. Electrical Systems • Extension cords are not permitted in labs except for temporary (one day) use. • Check to see that all power cords are in good condition. • Replace or repair those with cracked housing, missing grounding pugs, etc.

31. Electrical Systems Electrical panels should be labeled and must have clear access. Access will be important in the event there is an urgent need to shut power off to a particular appliance of area. Breaker panels for the lab may be locked.

32. Electrical Systems Any time rewiring or renovation is performed it is a good idea to check to see that all outlets are grounded and that the polarity is correct. A simple circuit checking tool can do this.

33. Emergency Shutoffs • Florida Statutes require that “Each space equipped with unprotected gas valves accessible to students has an approved master cut-off readily accessible to the teacher” The teacher should be aware of the location of the gas shut-offs in their laboratory classroom. Shutoff is sometimes accomplished with a quarter turn valve and sometimes with an electrical gas valve.

34. Safety Inspection Findings • Let’s look at some photos of laboratory inspections in schools. See how many problems you can find.

35. Safety inspection findings

36. Safety inspection findings Pathways blocked by trash Improperly disposal of chemicals

37. Safety Inspection findings

38. Safety Inspection findings • Exit door obstructed

39. Safety Inspection Findings

40. Safety Inspection Findings • Chemicals, wastes & incompatible stored together

41. Safety Inspection Findings

42. Extension cords should be avoided but certainly should never be suspended where the could be damaged or might snag on a passing cart etc.. Safety Inspection Findings

44. Check to ensure that heavy objects are stored no more than five feet off the floor. • Where appropriate, are ladders and/or step stools available and in good repair?

46. Nothing wrong here, a rigid container that can be sealed should be available for broken glass.

48. Mechanical hazards such as this open drive belt must be guarded.

50. This is a tricky one. Plastic tubing should not extend below the rim of a sink unless the faucet is equipped with an anti-siphon device (see arrow, inset). Soap and towels must be readily available.