Hazard Prevention and Engineering Controls: Traditional and Modern Approaches

Hazard Prevention and Engineering Controls: Traditional and Modern Approaches

Monday, June 1, 2015, 10:30 AM - 12:30 PM

CS-104-01 ​​​Key Elements of Temporary Release Shelter Programs: Development and Implementation

V. Aizenberg, ExxonMobil Biomedical Sciences, Baytown, TX

Situation/Problem: Emergency response plans for most sites dealing with acutely hazardous chemicals often include Temporary Release Shelters (TRS) as part of the response. Enabling key personnel to safely manage the emergency is intrinsic to safe site operations. However, some sites simply designate buildings as TRS (also known as Safe Havens and Shelters-in-Place) without specific effort to test their efficacy (tightness) and developing corresponding management programs. 

Resolution: This presentation shares key features of a well-designed and well-managed TRS program. These include: Design requirements for TRS HVAC systems and building envelopes; Testing of TRS building tightness (per ASTM E741-11) as well as architectural and engineering pre-requisites for such testing; Periodic TRS testing and maintenance program, and Stakeholder engagement

Results: Implementation of TRS programs of several buildings of various sizes (including before and after HVAC upgrades) will be illustrated and discussed. These include large office and administrative buildings, medium-size control buildings and smaller security areas. 

Lessons Learned: Examples of appropriate TRS as well as erroneous TRS arrangements will be re-emphasized. Advice on efficiently establishing and maintaining TRS will be provided. 

CS-104-02 Approaches to Dust Control in Mining

G. Joy, NIOSH Office of Mine Safety and Health Research, Pittsburgh, PA

Situation/Problem: Miners are at elevated risk of developing pneumoconioses as a result of exposure to airborne respirable dust in their work. This exposure originates from the extraction and subsequent processing and handling of the mined mineral. For the period 2003 - 2012, the portion of compliance samples in the metal/nonmetal industry for respirable quartz exceeding the occupational exposure limit (OEL) by commodity was: metallic minerals 18%; nonmetallic minerals 16%; sand & gravel 12%; and stone 11%. In coal mines, the fraction exceeding the OEL for respirable coal mine dust was 5%, and the fraction exceeding the quartz OEL was 13%. Between 1990 and 1999, 2,407 deaths in the United States were attributed to silicosis; of those, occupation information was available for 881 deaths. For those 881 deaths, employment in the metal/nonmetal mining industry accounted for 15%, and the most common occupation recorded was mining machine operator.

Resolution: Research by the U.S. Bureau of Mines – subsequently NIOSH – and many other organizations has identified feasible engineering controls for dust exposure in mining. These controls are extensions of the methods commonly used in non-mining industries with consideration of situations unique to mining. The primary methods applied are isolation and containment of the source and/or receptor, general and local exhaust ventilation, and application of water to prevent or suppress airborne dust. Regardless of the type of mineral pursued, similarities exist among the methods employed to recover and process it, permitting application of similar approaches to control dust.

Results: Selection and design of controls in mining is complicated by the scale size, quantities, and volume of mining processes, but proceeds in the normal fashion. One difference in mining is that the dust to be controlled may be the product of the process. When this is the case, recovering the collected dust in a usable form is an important consideration. Information will be presented on approaches to dust control, with comment on control design and selection issues.

Lessons Learned: Effective control of respirable dust exposure in mining is feasible in almost all situations through selection and application of appropriate engineering controls. As in all industries, sustaining initial control efficiencies requires an on-going program of oversight and verification.

SR-104-03 Use of Ventilation Fans for Reducing Worker Airborne Dust Exposures at a Steel Foundry in HaTay, Vietnam

G. Croteau, University of Washington, Seattle, WA

Objective: Establish effectiveness of using ventilation fans to reduce airborne dust exposures, determine effect on downwind exposure levels and develop best practice guidelines for utilizing this simple engineering control.

Methods: The use of fans for reducing airborne dust exposure levels was assessed at a steel foundry located in an open sided building in HaTay, Vietnam. A paired sample experimental design was utilized. Task based personal exposure levels were determined with and without the use of ventilation fans in order to maintain spatial and temporal continuity and reduce the effect of changing work conditions. Work activities included mold breakdown, sand sieving, and metal grinding tasks. Worker exposure levels were determined using a direct reading dust monitor; area dust levels were also determined 2.8 and 5.5 meters downwind. The fans were assessed as they are typically used at this workplace.

Results: A total of 11 paired task based samples (13 to 104 minutes in length) were obtained. A mean exposure reduction of 55.3% (SD 35.3%) was attained, based on 11 paired samples; a single paired sample indicated an exposure increase of 14.1%. Downwind dust levels (area samples) were 67% to 266% higher with the fan in use, with the exception of one of five paired samples. The fans, placed 1.5 to 10.0 meters from the worker, generated a mean air velocity of 142.5 meters/minute measured at the worker. The 0.6 and 2.6 kilowatt-hour fans had a mean volumetric flow rates of 133 and 269 cubic meters/minute.

Conclusions: The study results demonstrate fans are an effective means of reducing worker exposure levels. However, downwind effects need to be considered. Ideally, fans should be directed towards the outside in open sided buildings and never towards other workers. A lower velocity (30 meters/minute at the worker), less turbulent air flow might provide more effective exposure control.

SR-104-04 Self-Reported Use of Dust Controls in Stone Countertop Fabrication in High and Low Enforcement States

M. Philips, J. Canary, University of Oklahoma Health Sciences Center, Oklahoma City, OK

Objective: Fabrication of countertops from natural granite and quartz-based artificial stone has potential for serious overexposure to respirable crystalline silica if dust controls are not used. This study extended previous research on the prevalence of dry methods in granite countertop fabrication in Oklahoma to investigate whether dust controls were more commonly used in states with high levels of enforcement by occupational safety and health agencies.

Methods: Intensity of enforcement in each state was determined by dividing the number of silica emphasis inspections in stone product manufacturing establishments (SIC 3281) between January 2008 and June 2013 by the state’s population. Pairs of states within the same region with strongly contrasting levels of enforcement were chosen for comparison: Minnesota (4.15 silica inspections per million population) vs. Michigan (0) and New Mexico (5.34) vs. Arizona (0.63). One city in each state was selected for a census of stone countertop fabrication shops. The cities in each pair of states were similar in population. A complete enumeration of all granite and quartz countertop fabricators in each of these cities was attempted using Internet searches. A survey of fabrication and housekeeping methods was administered over the phone to a qualified individual at each shop.

Results: We identified 8 shops in Rochester MN, 3 shops in Ann Arbor MI, 11 shops in Albuquerque NM, and 15 shops in Tucson AZ. Shops in the low-enforcement states were significantly less willing to participate in the survey than shops in the high-enforcement states (28% vs. 84% participation, p = 0.0003). Among responding shops in the high-enforcement states, 69% reported that every step in the fabrication process was performed mostly or entirely wet, compared to 40% of responding shops in the low-enforcement states. This result was not statistically significant. Fabrication methods reported for granite and quartz surfacing were nearly identical.

Conclusions: Due to potential nonresponse bias, the relationship between degree of enforcement in a state and self-reported use of wet methods could not be determined. The reported prevalence of wet methods in the manufacturing of granite and quartz countertops in the high-enforcement states of Minnesota and New Mexico was much higher than the previously self-reported prevalence of wet methods in Oklahoma, a low-enforcement state.

SR-104-05 Efficiency of Intact and Damaged HEPA Filters and their Gaskets under Different Flowrate and Pressure Drop Conditions

F. Akbar-Khanzadeh, UT HSC College of Medicine, Toledo, OH; K. Smigielski, University of Toledo, Toledo, OH

Objective: High efficiency particulate air (HEPA) filter, a main element of industrial or domestic ventilation systems, can be damaged during handling and installation. Then, the question is how the damage would alter the performance of the filter. This project was to evaluate HEPA filter capture efficiency of intact or damaged gaskets and filters.

Methods: The filters (60 x 60 x 29 cm) for: (a) “gasket testing” used PTFE with one piece poured gasket; and, (b) “filter testing” used glass fiber, with a dove tail gasket. Poly Alpha Olefin particulate was used as aerosol challenge. Aerosol generators with specific nozzles were to generate known diameter (e.g., 0.3 µm) particles. A counter instrument was used to count the particles at the inlet and outlet of a custom designed filter housing. Each finally reported count was an average of 6 readings. Known diameter holes to the gasket and filter were created by using a set of standard cylinders. The gaskets and filters were tested within the filter housing at two system airflows (28.3x103 and 56.6x103 L/min) and two pressure drops (25 and 50 mm water gauge). Gaskets and filters were tested under following conditions: (1) best fit: no known gasket or filter leak, and (2) man-made holes: gaskets and filters with 6 sizes man-made holes of 0.5, 0.8, 1.6, 3.2, 4.8 and 6.4 mm diameters.

Results: The best fit HEPA filter performed at capture efficiency of more than 99.99%. Particle leakage increased with the diameter of hole. However, at 0.5, 0.8 and 1.6 mm diameter holes the capture efficiency remained above 99.99%. At 3.2 mm hole the efficiency dropped to 99.98% and at 4.8 and 6.4 mm holes the capture efficiency dropped below the HEPA quality capture efficiency of 99.97%.

Conclusions: The capture efficiency of HEPA filters remained above 99.97% at or smaller than 3.2 mm hole in either gasket or filter media. Additional tests are recommended to further verify these findings.

CS-104-06 Carbon Dioxide Exposures at Meat Batching Operations

M. Wiggins, Liberty Mutual Insurance, Lexington, SC

Situation/Problem: Liquid carbon dioxide is used at meat product batching operation in order to cool the meat so that it can be formed into nuggets or patties. As meat product is loaded into the batch mixer(s) along with liquid flavorings, it is necessary to inject liquid carbon dioxide into the meat mixture within the batch mixer. If this injection process is not properly contained/ventilated, excess carbon dioxide vaporizes and is released into the work room. Resulting exposures can exceed applicable exposure limits.

Resolution: Carbon dioxide levels were measured using an appropriate direct reading instrument. Employee exposures were measured using passive diffusion tubes. Based on the initial survey, excessive exposures were determined. Survey also identified sources of excessive exposures so that corrective actions could be considered and implemented.

Results: Initial measurements of process indicated that exposures can exceed the applicable exposure limits. After modifications are made to process, exposures were reduced to levels that were well below the applicable exposure limits.

Lessons Learned: Excessive exposures at this operation were due to: Leakage of carbon dioxide gas into the work room due to excessive volume of liquid than could be removed by the exhaust ventilation system; Inadequate seal between the batch mixer lid cover on the top of the batch mixer hopper; and lack of control of flow and volume of liquid carbon dioxide into the batch mixer. Excessive exposures were corrected with the following process controls: Assure that the exhaust system is not clogged. (Carbon dioxide can sublime and deposit within the exhaust duct causing obstruction of the ducts and causing the exhaust fan to freeze; Assure a tight seal around the batch mixer during carbon dioxide injection; Control the volume, distribution and flow rate of the liquid carbon dioxide into the batch mixer to prevent excess volume of carbon dioxide in to the batch mixer. Control of flow rate and distribution of carbon dioxide allows carbon dioxide to be better absorbed by the batch (meat product).