Safety Work

OSH 3001, Fundamentals of Occupational Safety and Health 1

Course Learning Outcomes for Unit V Upon completion of this unit, students should be able to:

5. Recommend strategies for the control of common workplace hazards.

5.1 Develop a plan for the recognition, evaluation, and control of workplace health hazards.

6. Apply hazard assessment tools as they relate to industrial hazards. 6.1 Select methodologies to identify and evaluate workplace health hazards.

Course/Unit Learning Outcomes

Learning Activity

5.1 Chapter 16 Chapter 18 Unit V Scholarly Activity

6.1

Unit V Lesson Chapter 16 Chapter 18 Unit V Scholarly Activity

Reading Assignment Chapter 16: Industrial Hygiene and Confined Spaces Chapter 18: Noise and Vibration Hazards

Unit Lesson This lesson and the reading assignments will discuss industrial hygiene, confined spaces, noise and vibration hazards, and blood-borne pathogens. Industrial hygiene is the science of anticipating, recognizing, evaluating, and controlling occupational health hazards. Occupational health hazards include but are not limited to physical, chemical, biological, noise, and ergonomic. Professional industrial hygienists (IH) have advanced degrees typically in a science or medical field or professional certifications, such as the Certified Industrial Hygienist (CIH) designation or both. The majority of smaller employers will not have an IH on staff. In these cases, they will contract an IH from an outside source, when needed, or the safety professional will assume IH responsibilities. Industrial hygienists use environmental monitoring and analytical methods to determine the extent of exposure to an employee. There are a number of monitoring and measurement tools that are used for this purpose.

UNIT V STUDY GUIDE

Industrial Hygiene, Confined Spaces, Noise, and Vibration

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Colorimetric Detector Tubes Colorimetric detector tubes, also known as stain tubes, are graduated glass tubes that are filled with a material that will react and change colors when it comes into contact with a specified contaminant. The tubes are sealed at both ends until ready to use. Prior to using, the IH will snap the tips from both ends. The tube will then be inserted into a manual hand pump. As the air is drawn through the chemical reagent in the tube, the reagent reacts and changes color. The length of the color change that occurs is proportional to the concentration and is measured using the graduated markings on the side of the glass tube (Interscan, 2012). Colorimetric detector tubes are used only as a screening instrument to determine if further testing is warranted. They cannot be used for continuous monitoring. Additionally, the tubes are substance-specific. This means that you must have some idea what contaminant may be present in order to choose the correct tube to use. Colorimetric tubes have expiration dates, and some may have to be refrigerated. Photoionization Detector Photoionization detectors (PIDs) are meters that are used to detect volatile organic compounds (VOCs). VOCs include solvents, fuels, and many other toxic substances that are comprised of organic molecules. The PID is a broad range detector that measures the aggregate reading of the total VOCs in a given air sample. The PID uses high energy ultraviolet light from a lamp contained in the detector to knock electrons from the VOC molecules as they pass by in the air stream. The fragments (ions) are collected on electrically charged plates, which produce a flow of electrical current in proportion to the concentration of the VOCs in the sample. The amount of energy needed to remove an electron from the VOC molecule is called the ionization potential or IP, which is measured in electron volts (eV). As long as the lamp energy is greater than the IP, the molecule will be detected. IPs of specific VOCs, where available, can be found in the National Institutes for Occupational Safety and Health (NIOSH, n.d.) Pocket Guide to Chemical Hazards. PID manufacturers can also provide this information as a part of their technical support documents and manuals. Keep in mind that the PID does not tell you whether there is a particular contaminant in the air sample, nor will it tell you the relative concentrations of specific VOCs. It will, however, allow you to accurately judge the total VOC concentration. Flame Ionization Detector Flame ionization detectors (FIDs) detect VOCs by igniting the chemicals contained within an air sample as it passes over a hydrogen-air flame. Unlike the PID, the FID uses the hydrogen-air flame instead of the ultraviolet light source to break electrons off the organic molecules. It then collects the free electrons on electrically charged plates, which produce a flow of electrical current in proportion to the concentration of VOCs in the sample. FIDs are able to detect a wider range of VOCs and are not as susceptible as PIDS to humidity interference. FIDs are not used as frequently as PIDs due to presence of an actual flame. Multi-Gas Meter Multi-gas meters are used when entering spaces that could contain hazardous atmospheres, such as confined spaces. At a minimum, a four-gas meter should be used to evaluate hazardous atmospheres within a confined space. These four-gas meters will test oxygen, lower explosive limit (LEL), and toxins (typically hydrogen sulfide and carbon monoxide). Oxygen levels must be within the 19.5%–23.5% parameter and must be measured first. The reason behind this is two-fold. If we have an oxygen deficient atmosphere (below 19.5%), it is considered immediately dangerous to life and health (IDLH) and can only be entered using supplied air and with proper rescue services available. Secondly, if the proper oxygen content is not present,

Air sampling hand pump with colorimetric tube inserted. (OSHA, n.d.)

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the sensors within the meter that detect the flammables and toxics will not read accurately. These sensors depend on the oxygen content for proper detection. The multi-gas meter should appropriately be set to alarm for the following parameters:

 oxygen (O2) = 19.5% to 23.5%,

 LEL = less than 10%,

 hydrogen sulfide (H2S) = less than 10 parts per million (ppm), and

 carbon monoxide (CO) = less than 35 ppm.

In addition to these baseline parameters, a multi-gas meter should have the capability to measure specific concentrations of other toxic gases or vapors that may be present. These instruments must be calibrated properly to ensure proper readings. Passive Sampling Badges Passive sampling badges (PSBs) or passive diffusive sampling requires no electricity, no pump, and no moving parts. They are easy to use and require no calibration. Passive sampling relies on the unassisted molecular diffusion of gases through a diffusive surface onto an absorbent. The PSB is worn near the shirt collar area, putting it within the breathing zone. The gases diffuse at a fixed rate. After the sampling period is completed, the badge is capped and sent to an analytical laboratory for desorption of contaminant molecules from the collection pad using a solvent and then analyzed by gas chromatography. Using the elapsed time (start and end times) during the sampling period and the contaminant volume detected from the laboratory analysis, a time-weighted average exposure can be calculated. Passive sampling badges are available for a variety of different chemical agents (Millipore Sigma, n.d.). Active Sorbent Tube and Particulate Samplers Sorbent tube and particulate sampling require the use of a pump to draw air through a collection device. When using sorbent tubes, gas- or vapor-phase contaminant molecules are pulled through a glass tube filled with filter media (e.g., charcoal, silica gel, tenax) at a constant flow rate using a low, medium, or high flow pump over a specific period of time (Casella, n.d.). The contaminant molecules adhere to the filter media during the sampling period. At the end of the sampling, the ends of the glass tubes are capped, and the tubes are submitted to a laboratory for analyses for the particular contaminant of concern. Active sampling of this type requires that the pump being used be calibrated at a constant flow rate over a specific time period. However, particulate sampling media is in cassette form and has a filter media that is designed to trap specific sized particles on the surface while allowing smaller particles to pass through (Casella, n.d.). Common filter media for particulate sampling include mixed cellulose ester (MCE), which is used for metals, welding fumes, asbestos, and other fibers; polyvinyl chloride (PVC), which is used for silica, respirable/total dust and chromates; and polytetrafluorethylene (PTFE), which is used for PM10, pesticides, aerosolized acids, and solvents. After sampling is complete, the cassette is removed and sent to a laboratory for gravimetric (pre- and post-weight comparison) and/or specific contaminant volume analysis.

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Noise Dosimeter A noise dosimeter is similar to a sound level meter in that it can be used to measure sound/noise levels. However, a dosimeter is actually a sampling meter that is most often used to measure an employee’s exposure (dose) to noise during a specific sampling period or work shift. A noise dosimeter is placed on a worker with a microphone clipped in his/her hearing zone, a two-foot sphere around the head. The dosimeter can calculate the employee’s noise exposure in real-time by using standard noise calculations. Noise dosimeters give measurements in average decibels (dB) over a specific period of time. Sound Level Meter A sound level meter (SLM) is one of the methods used to measure noise. SLMs can be used to check the accuracy of dosimeter readings, identify noise sources that may require abatement measures, and assess the efficacy of noise abatement engineering controls. Some SLMs may have measurement modes that allow for measurement of transient (peak or impulse) sounds. SLMs read in decibels (dB) at a specific moment in time. SLMs cannot be used to comply with requirements for full-shift monitoring. This must be done with noise dosimeters.

Heat Stress/Heat Index Monitor Heat stress is a common hazard—especially in workplaces located in hotter climates or with a significant portion of strenuous work performed outdoors during the summer months. A heat stress monitor measures different types of temperatures (dry-bulb, natural wet-bulb, and radiant heat), air movement, and humidity and performs a conversion to what is commonly called wet bulb globe temperature (WBGT). WBGT is a measurement of heat stress in the direct sun (National Weather Service, 2011). Some heat stress monitors can also calculate heat index (HI), which only takes into account temperature and humidity and is applicable to shaded areas. To obtain accurate measurements, heat stress monitors should be located at the employee’s chest height and be given enough time to allow all of the readings to stabilize. Time-weighted average (TWA) WBGT calculations are useful in helping to assess potential employee over-exposure and to help formulate work-rest regimens.

References

Casella. (n.d.). Introduction to personal air sampling. Retrieved from http://airsamplingsolutions.com/index.php/introduction-to-personal-air-sampling/

Interscan. (2012). Detector tubes and when to use them. Retrieved from

http://www.gasdetection.com/knowledge-base/best-practices/detector-tubes-and-when-to-use-them/ Kardous, C. (2017). NIOSH Sound Level Meter app [Photograph]. Retrieved from

https://commons.wikimedia.org/wiki/File:NIOSHSoundLevelMeterAppTesting.jpg Millipore Sigma. (n.d.). Passive (diffusive) sampling overview. Retrieved from

http://www.sigmaaldrich.com/analytical-chromatography/air-monitoring/passive-sampling.html National Institute for Occupational Safety and Health. (n.d.). NIOSH pocket guide to chemical hazards.

Retrieved from https://www.cdc.gov/niosh/npg/default.html National Weather Service. (2011). Wetbulb globe temperature. Retrieved from

https://www.weather.gov/tsa/wbgt

Sound Level Meter app being tested at NIOSH (Kardous, 2017)

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Occupational Safety and Health Administration. (n.d.). Figure 1. Proper insertion of detector tube into pump [Photograph]. Retrieved from https://www.osha.gov/dts/osta/otm/otm_ii/images/chpt3_fig1.jpg

Suggested Reading Read the resources linked below for more information on hearing conservation and permissible exposure limits, and safety and health topics focused on direct-reading instruments and blood-borne pathogens. Occupational Safety and Health Administration. (n.d.). Hearing conservation. Retrieved from

https://www.osha.gov/Publications/OSHA3074/osha3074.html Occupational Safety and Health Administration. (n.d.). Permissible exposure limits—Annotated tables.

Retrieved from https://www.osha.gov/dsg/annotated-pels/ Occupational Safety and Health Administration. (n.d.). Direct-reading instruments. Retrieved from

https://www.osha.gov/SLTC/directreadinginstruments/index.html Occupational Safety and Health Administration. (n.d.). Bloodborne pathogens and needlestick prevention.

Retrieved from https://www.osha.gov/SLTC/bloodbornepathogens/index.html