Operator's Breathing Zone Research Articles

Characterization and Control of Airborne Particles Emitted During Production of Epoxy/Carbon Nanotube Nanocomposites

This work characterized airborne particles generated from the weighing of bulk, multiwall carbon nanotubes (CNTs) and the manual sanding of epoxy test samples reinforced with CNTs. It also evaluated the effectiveness of three local exhaust ventilation (LEV) conditions (no LEV, custom fume hood, and biosafety cabinet) for control of particles generated during sanding of CNT-epoxy nanocomposites. Particle number and respirable mass concentrations were measured using an optical particle counter (OPC) and a condensation particle counter (CPC), and particle morphology was assessed by transmission electron microscopy. The ratios of the geometric mean (GM) concentrations measured during the process to that measured in the background (P/B ratios) were used as indices of the impact of the process and the LEVs on observed concentrations. Processing CNT-epoxy nanocomposites materials released respirable size airborne particles (P/B ratio: weighing = 1.79; sanding = 5.90) but generally no nanoparticles (P/B ratio ∼1). The particles generated during sanding were predominantly micron sized with protruding CNTs and very different from bulk CNTs that tended to remain in large (>1 μm) tangled clusters. Respirable mass concentrations in the operator's breathing zone were lower when sanding was performed in the biological safety cabinet (GM = 0.20 μg/m3 compared with those with no LEV (GM = 2.68 μg/m3 or those when sanding was performed inside the fume hood (GM = 21.4 μg/m3; p-value < 0.0001). The poor performance of the custom fume hood used in this study may have been exacerbated by its lack of a front sash and rear baffles and its low face velocity (0.39 m/sec).

Safety observation contributions to a glovebox safety program

Programmatic operations at the Los Alamos National Laboratory Plutonium Facility (TA-55) involve working with various amounts of plutonium and other highly toxic, alpha-emitting materials. The spread of radiological contamination on surfaces, airborne contamination, and excursions of contaminants into the operator's breathing zone are prevented through the use of a variety of gloveboxes (the glovebox, coupled with an adequate negative pressure gradient, provides primary confinement). The TA-55 Glovebox Safety Program (GSP) augments this passive safety feature. In an effort to increase safety awareness and to decrease accidents and incidents, a behavior-based safety observation program (ATOMICS) focusing on the identification and elimination of at-risk behaviors was initiated. Workers are trained on how to conduct safety observations and given guidance on specific behaviors to note. This paper focuses on collection of data from glovebox work observation cards related to the GSP, incorporation of this information into output metrics, and examples of how the use of these metrics has improved the GSP. This effort contributes to the Los Alamos National Laboratory's Continuous Improvement Program by providing information that can be used to improve operational safety.

Lean Six Sigma Tools for a Glovebox Glove Integrity Program

Programmatic operations at the Los Alamos National Laboratory (LANL) Plutonium Facility involve working with various amounts of plutonium, uranium, and other highly toxic, alpha-emitting materials. The spread of radiological contamination on surfaces, airborne contamination, and excursions of contaminants into the operator's breathing zone are prevented through use of a variety of gloveboxes. Evaluation of the glovebox configuration shows that the glovebox gloves are the most vulnerable part of this engineering control. Recognizing this vulnerability, the Glovebox Glove Integrity Program was developed to minimize or prevent glovebox glove events, namely, loss of confinement of the glovebox through an unplanned opening in the glovebox glove. In addition, LANL established the Lean Manufacturing and Six Sigma business practices (LSS) program to effectively improve administrative and engineering controls and work processes. The LSS tools were developed to analyze, optimize, and manage glovebox glove process performance with meaningful data. This includes identifying process scope and ownership and measuring performance. This paper discusses LSS tools, provides examples of LSS tools, and shows how managers use the results to make decisions. This effort contributes to LANL Continuous Improvement Program by providing information that improves the efficiency, cost effectiveness, and formality of glovebox operations.

Airborne Nanoparticle Exposures while Using Constant-Flow, Constant-Velocity, and Air-Curtain-Isolated Fume Hoods

Tsai et al. (Airborne nanoparticle exposures associated with the manual handling of nanoalumina and nanosilver in fume hoods. J Nanopart Res 2009; 11: 147-61) found that the handling of dry nanoalumina and nanosilver inside laboratory fume hoods can cause a significant release of airborne nanoparticles from the hood. Hood design affects the magnitude of release. With traditionally designed fume hoods, the airflow moves horizontally toward the hood cupboard; the turbulent airflow formed in the worker wake region interacts with the vortex in the constant-flow fume hood and this can cause nanoparticles to be carried out with the circulating airflow. Airborne particle concentrations were measured for three hood designs (constant-flow, constant-velocity, and air-curtain hoods) using manual handling of nanoalumina particles. The hood operator's airborne nanoparticle breathing zone exposure was measured over the size range from 5 nm to 20 mum. Experiments showed that the exposure magnitude for a constant-flow hood had high variability. The results for the constant-velocity hood varied by operating conditions, but were usually very low. The performance of the air-curtain hood, a new design with significantly different airflow pattern from traditional hoods, was consistent under all operating conditions and release was barely detected. Fog tests showed more intense turbulent airflow in traditional hoods and that the downward airflow from the double-layered sash to the suction slot of the air-curtain hood did not cause turbulence seen in other hoods.

European and International Standards on health and safety in welding

A number of European and International Standards on health and safety in welding have been published in recent years and work on several more is nearing completion. These standards have been prepared jointly by the International Standards Organization (ISO) and the European Committee for Standardization (CEN). The standards development work has mostly been led by CEN/TC 121/SC 9, with excellent technical input from experts within Europe; but work on the revision of published standards, which has recently gathered pace, is now being carried out by ISO/TC 44/SC 9, with greater international involvement. This paper gives an overview of the various standards that have been published, are being revised or are under development in this field of health and safety in welding, seeking to (i) increase international awareness of published standards, (ii) encourage wider participation in health and safety in welding standards work and (iii) obtain feedback and solicit comments on standards that are currently under development or revision. Such an initiative is particularly timely because work is currently in progress on the revision of one of the more important standards in this field, namely EN ISO 10882:2001 Health and safety in welding and allied processes— Sampling of airborne particles and gases in the operator's breathing zone — Part 1: Sampling of airborne particles.

Elements of a Glovebox Glove Integrity Program

Programmatic operations at the Los Alamos National Laboratory Plutonium Facility involve working with various amounts of plutonium and other highly toxic, alpha-emitting materials. The spread of radiological contamination on surfaces and airborne contamination and excursions of contaminants into the operator's breathing zone are prevented through the use of a variety of gloveboxes. The glovebox gloves are the weakest part of this engineering control. As a matter of good business practice, a team of glovebox experts from Los Alamos National Laboratory has been assembled to proactively investigate processes and procedures that minimize unplanned openings in the glovebox gloves, i.e., breaches and failures. Working together, they have developed the key elements of an efficient Glovebox Glove Integrity Program (GGIP). In the following report, the consequences of a glove failure or breach are identified, the acceptable risk is clarified, and elements needed to implement an efficient GGIP are discussed.

Radiological assessment of petroleum pipe scale from pipe-rattling operations.

Petroleum pipe scale, consisting of concentrated inorganic solids such as barium sulfate, can deposit on the inside of down-hole pipes during the normal course of oil field pumping operations. A portion of this scale has been shown to contain naturally occurring radioactive materials (NORM), predominantly compounds of radium. When these pipes are removed from the well, there is a potential for radiation doses to the oil field workers handling the pipes, especially as the pipes are cleaned for reuse. A thorough sampling and measurement protocol was applied under a variety of weather conditions in an outdoor laboratory to obtain an accurate indication of the radiological and aerodynamic characteristics of scale release and dust dispersion during petroleum pipe scale removal from out-of-service pipes with a restored, historically relevant outdoor pipe-cleaning machine. Exposure rate data were also obtained for both the pre-cleaned pipes, and the general area inhabited by workers during the descaling operation. Four radiation exposure pathways were investigated: inhalation of pipe scale dust generated during pipe rattling, incidental ingestion of the pipe scale dust, external exposure from uncleaned pipes, and external exposure from pipe scale dispersed on the ground. Pipes from three oil fields were rattled to collect as much industry-representative data as possible. The Ra specific activity of the pipe scale ranged from 33.6 +/- 0.4 to 65.5 +/- 0.7 Bq g, depending on the formation. A median atmospheric dust loading of 0.13 mg m was measured in the operator breathing zone. The respirable fraction was observed to be about 42% to 46%. Based on cleaning 20 pipes per day,250 d per year on average, annual committed effective doses for the operator and helper ranged from 0.11 mSv (11 mrem) to 0.45 mSv(45 mrem) for inhalation and from 19 microSv (1.9 mrem) to 97 microSv (9.7 mrem) for incidental ingestion. Worker annual external dose from the pipe racks ranged from 0 to 0.28 mSv (28 mrem). In the deposition experiment, more than 99% by weight of the deposited scale fell within 2 m of the machine centerline, the vast majority of which was in the downwind direction. The dose from this deposited material dominated the worker dose estimates. The annual external dose from dispersed material was estimated to be 2.8 mSv (280 mrem) for the operator and 4.1 mSv (410 mrem) for the helper.

Effectiveness of passive gas-scavenging canisters attached to isoflurane anesthesia systems under standard-use conditions in a laboratory animal facility

Chronic exposure to trace levels of waste anesthetic gases has been linked to higher incidences of neurologic and reproductive dysfunction, hepatic and renal toxicity, and neoplasia in health care professionals. We have shown that low levels of isoflurane emissions are likely in conventional laboratory animal treatment rooms during the use of standard anesthesia delivery systems equipped with activated charcoal canisters for passive gas scavenging. In the present study, we surveyed the effectiveness of canisters (attached to well-maintained precision isoflurane vaporizers) in current use throughout our AAALAC-accredited laboratory animal facility. Canisters (Omnicon f/air) had been weighed prior to use and then attached to dual-loop systems (face mask and induction box circuits) from 1 week to 6 months of service. Isoflurane emissions were measured using a pre-calibrated, portable infrared spectrophotometer by attaching each canister to the face-mask circuit, occluding the face mask and closing the stopcock to the induction circuit, and running the system at uniform isoflurane concentration (2%) and oxygen flow rate (1 L minute−1). Samples were taken in animal procedure rooms (size range, 45–80 m3) in which the air turnover rate ranged between 20 and 30 nonrecirculating changes per hour. Nine of the 60 canisters (15%) in current use were found to have exceeded the manufacturer's recommended use-life (defined as a weight increase of 50 g). Of these nine, seven canisters did not scavenge isoflurane at all (indicated by emissions greatly exceeding 100 ppm). Isoflurane was not detected in the operator's breathing zone under normal use conditions (i.e. gas directed to both circuits at once). Of the 51 canisters that had not exceeded their rated use-life, 12 (23.5%) exhausted isoflurane at >2 ppm. Our data show that (i) the potential for exposure to waste isoflurane emissions will depend on the configuration of the delivery system and that (ii) enhanced attention to canister surveillance may be warranted even in well-run facilities.

Suppression of Pool Fires Using Halocarbon Streaming Agents

Handheld FM-200, FE-36, CF3I and Halotron I extinguishers with 2B:C, 5B:C and 10B:C ratings (or equivalent) were tested for extinguishing Class B heptane pool fires in small and large enclosures (45, 120 and 21000 m3). Test results showed that the Halotron I and CF3I extinguishers performed better than the FE-36 and FM-200 extinguishers. The concentrations of the halocarbons and acid gas by-products in the operator breathing zone and surroundings were measured during the tests. Measurements showed that the agent concentrations were below the levels that would pose life or health risk to the operator. The concentrations of acid gas by-products generated during suppression, however, were at dangerous levels in the small enclosures (45 and 120 m3). Heat flux towards the operator was also measured. Heat exposure presented a severe hazard to the operator during the pool fire suppression. Test results indicate some potentially hazardous conditions to an unprotected operator.

Aerosols generated during beryllium machining.

Some beryllium processes, especially machining, are associated with an increased risk of beryllium sensitization and disease. Little is known about exposure characteristics contributing to risk, such as particle size. This study examined the characteristics of beryllium machining exposures under actual working conditions. Stationary samples, using eight-stage Lovelace Multijet Cascade Impactors, were taken at the process point of operation and at the closest point that the worker would routinely approach. Paired samples were collected at the operator's breathing zone by using a Marple Personal Cascade Impactor and a 35-mm closed-faced cassette. More than 50% of the beryllium machining particles in the breathing zone were less than 10 microns in aerodynamic diameter. This small particle size may result in beryllium deposition into the deepest portion of the lung and may explain elevated rates of sensitization among beryllium machinists.

Carbon Monoxide Exposures during the Use of Propane-Powered Floor Burnishers

Abstract Custodians' exposures to carbon monoxide were monitored during the use of propane-powered floor burnishers to assess the health hazard risk to operators. Real-time carbon monoxide detectors with data logging capabilities were placed on the burnishers in the breathing zone of operators during burnisher use. Carbon monoxide levels were recorded every 30 seconds. Ventilation and physical characteristics of the spaces of burnisher use were characterized, as were burnisher maintenance practices. Sixteen burnishing events were monitored in total. Of the 16, 10 resulted in carbon monoxide exposures exceeding the 1989 Occupational Safety and Health Administration's permissible exposure limit and the National Institute for Occupational Safety and Health's recommended exposure limit of 200 ppm carbon monoxide as a ceiling. Thirteen of the 16 events resulted in exposures exceeding the more conservative American Conference of Governmental Industrial Hygienists not-to-exceed excursion limit of 125 ppm (five t...

Influence of Operatory Size and Nitrous Oxide Concentration Upon Scavenger Effectiveness

Concern regarding environmental health hazards for dental personnel chronically exposed to waste nitrous oxide (N2O) prompted this investigation. The influence on ambient N2O levels of scavenging, operatory size, and N2O concentration delivered to the patient was evaluated during treatment of 36 pediatric dental patients. The results showed that scavenging significantly reduced ambient N2O levels measured at 50-56 cm from the patient's nose. Scavenged ambient N2O levels were also observed to decrease when N2O concentrations administered to the patient were reduced from 50 to 30%. This concentration effect was not observed in the non-scavenged groups. ANOVA showed that operatory size exerted a non-significant influence on ambient N2O. The data collected during routine treatment of pediatric dental patients demonstrated that the scavenging system tested significantly reduced waste N2O in the operator's breathing zone, nearly approximating the 25-ppm recommendation established by the National Institute for Occupational Safety and Health (NIOSH).

Dust Control with Clean Air from an Overhead Air Supply Island (OASIS)

Abstract The objective of this work was to test the dust control effectiveness of an Overhead Air Supplied Island (OASIS). This device provides an envelope of clean air for dust protection for individual work stations in environments where other engineering controls are not practical or available. A fan powered filtration unit and a unique air distribution system provide 6000 cubic feet per minute of clean air over the operator. RAM-1 light scattering dust monitors were used to measure dust concentrations as the unit was turned on and off at a bagging machine operator's work station at two industrial silica plants. Dust concentration reductions at the operator's breathing zone were 98 and 82 percent, and dust concentrations never exceeded 0.06 mg/m3 during operation of the OASIS. The OASIS has potential applications in many industrial areas where dust exposures are excessive. It is a simple, self-contained unit which can reduce worker exposure to dust at a work station. In addition to the health benefits ...

A modified anaesthetic vapour extraction system.

A number of design modifications have been made to an extraction system for use with inhalation anaesthesia techniques in rats and other small laboratory animals. These changes necessitated a re-evaluation of the effectiveness of this equipment in limiting the operator's exposure to the anaesthetic vapours used. With a given fresh gas flow, the halothane vapour concentration in the operator's breathing zone was dependent on the design of the oronasal mask. With the optimum configuration the atmospheric concentration of halothane was less than 1 ppm.

Novel Engineering Methods for Ozone Reduction in Gas Metal Arc Welding of Aluminum

Gas metal arc welding (GMAW) of aluminum results in the emission of ultraviolet radiation which then causes the production of ozone and nitrogen dioxide. Two novel methods were developed; one to suppress the ozone at the arc, and one to suppress it for protection of nearby personnel while providing a controlled flow of local ventilation to minimize ozone reaching the operator's breathing zone. Without these control methods, the ozone levels were in excess of the TLV® of 0.1 ppm, but with these devices, the levels were maintained well below the TLV.

Evaluation of a scavenging system for use with inhalation anaesthesia techniques in rats.

A minimum fresh gas flow of 1 litre per minute per mask and an inspired concentration of 2-3% halothane was required in induce anesthesia in rats in 1-2 min. Anaesthesia was maintained with an inspired concentration of 1.5-2% halothane. Arterial carbon dioxide concentration increased during anaesthesia and was reduced by increasing the flow of fresh gas. Using the apparatus described here, halothane vapour concentration in the operator's breathing zone was 5 ppm. Prior to its introduction, levels of 250 ppm had been recorded in a poorly-ventilated animal room.

Ozone production from photocopying machines.

Ten photocopying machines of different makes and models were tested for ozone emissions. All but one produced detectable amounts. Concentrations at operator's breathing zone varied from less than 4 to 300 micrograms/m3, which corresponded to emission rates of less than 1 to 54 micrograms/copy. Servicing reduced emissions to less than 1.4 micrograms/copy, but preservicing levels were retained after several weeks of operation.

A GUIDE TO THE DESIGN AND INSTALLATION OF LABORATORY FUME CUPBOARDS&lt;xref ref-type="fn" rid="fn1"&gt;&lt;sup&gt;*&lt;/sup&gt;&lt;/xref&gt;

After reviewing available information and carrying out appropriate tests, the Working Party has recommended that a correct aerodynamic design of fume cupboard will require an air velocity of 0.5 m/s under working conditions. Variations in air velocity across the working face should not exceed ±15%. If it is essential that under no circumstances should transient escapes of material take place in the operator's breathing zone, a face velocity of 0.76 m/s may be necessary. Under these conditions the use of a total enclosure is preferred. The Guide includes recommendations for the design and installation of fume cupboards to meet these criteria.

Mercury hazard and its control during operation of fluorescent tube breakers.

The use of commercially available tube breakers to crush large numbers of fluorescent light tubes for easier disposal was found to produce potentially hazardous mercury concentrations in the air in the vicinity of the operation. Concentrations varied from negligible to more than 1 mg Hg per cubic meter. Exposures in the operator's breathing zone were mostly below the acceptable limits, however the potential for excessive concentrations was demonstrated. A system for control of the hazard by local exhaust ventilation was devised.