Nasal Ranger Field Olfactometers Research Articles

Instrumental measurement of odour nuisance in city agglomeration using electronic nose

The paper describes an operation principle of odour nuisance monitoring network in a city agglomeration. Moreover, it presents the results of investigation on ambient air quality with respect to odour obtained during six-month period. The investigation was carried out using a network comprised of six prototypes of electronic nose and Nasal Ranger field olfactometers employed as a reference method. The monitoring network consisted of two measurement stations localized in a vicinity of crude oil processing plant and four stations localized near the main emitters of volatile odorous compounds such as sewage treatment plant, municipal landfill, phosphatic fertilizer production plant. The electronic nose prototype was equipped with a set of six semiconductor sensors by FIGARO Co. and one PID-type sensor. The field olfactometers were utilized for determination of mean concentration of odorants and for calibration of the electronic nose prototypes in order to provide their proper operation. Mean monthly values of odour concentration depended on the site of measurement and on meteorological parameters. They were within 0 – 6.0 ou/m3 range. Performed investigations revealed the possibility of electronic nose instrument application as a tool for monitoring of odour nuisance.

Evaluation of Ambient Air Odour Quality in Vicinity of Municipal Landfill Using Electronic Nose Technique

The paper presents the results of investigation on ambient air quality evaluation with respect to concentration of odorants in a vicinity of municipal landfill. The investigation was carried out with a prototype of electronic nose and a team of panelists utilizing the Nasal Ranger field olfactometers. The prototype was equipped with a set of six semiconductor sensors by FIGARO Co. and one PID-type sensor. Performed measurements revealed that the prototype of electronic nose could be employed for determination of odorants concentration in ambient air; difference in mean values of odorants concentration obtained with both techniques was statistically insignificant in 75% of cases. The highest mean values of odorants concentration amounted from 12.5 to 36.7 ou/m3 depending on distance from the emitter, measurement direction and applied measurement technique.

Odorants and Malodors Associated with Land Application of Biosolids Stabilized with Lime and Coal Fly Ash

Malodor emissions limit public acceptance of using municipal biosolids as natural organic resources in agricultural production. We aimed to identify major odorants and to evaluate odor concentrations associated with land application of anaerobically digested sewage sludges (Class B) and their alkaline (lime and coal fly ash)-stabilized products (Class A). These two types of biosolids were applied at 12.6 tonnes ha(-1) (dry weight) to microplots of very fine clayey Vertisol in the Jezreel Valley, northern Israel. The volatile organic compounds (VOCs) emitted from the biosolids before and during alkaline stabilization and after incorporation into the soil were analyzed by headspace solid-phase microextraction followed by gas chromatography-mass spectrometry. Odor concentrations at the plots were evaluated on site with a Nasal Ranger field olfactometer that sniffed over a defined land surface area through a static chamber. The odors emitted by anaerobically digested sewage sludges from three activated sludge water treatment plants had one characteristic chemical fingerprint. Alkaline stabilization emitted substantial odors associated with high concentrations of ammonia and release of nitrogen-containing VOCs and did not effectively reduce the potential odor annoyance. Odorous VOCs could be generated within the soil after biosolids incorporation, presumably because of anaerobic conditions within soil-biosolids aggregates. We propose that dimethyl disulfide and dimethyl trisulfide, which seem to be most related to the odor concentrations of biosolids-treated soil, be used as potential chemical markers for the odor annoyance associated with incorporation of anaerobically digested sewage sludges.

Field Olfactometry Assessment of Dairy Manure Land Application Methods

Surface application of manure in reduced tillage systems generates nuisance odors, but their management is hindered by a lack of standardized field quantification methods. An investigation was undertaken to evaluate odor emissions associated with various technologies that incorporate manure with minimal soil disturbance. Dairy manure slurry was applied by five methods in a 3.5-m swath to grassland in 61-m-inside-diameter rings. Nasal Ranger Field Olfactometer (NRO) instruments were used to collect dilutions-to-threshold (D/T) observations from the center of each ring using a panel of four odor assessors taking four readings each over a 10-min period. The Best Estimate Threshold D/T (BET10) was calculated for each application method and an untreated control based on preapplication and <1 h, 2 to 4 h, and approximately 24 h after spreading. Whole-air samples were simultaneously collected for laboratory dynamic olfactometer evaluation using the triangular forced-choice (TFC) method. The BET10 of NRO data composited for all measurement times showed D/T decreased in the following order (a = 0.05): surface broadcast > aeration infiltration > surface + chisel incorporation > direct ground injection Sshallow disk injection > control, which closely followed laboratory TFC odor panel results (r = 0.83). At 24 h, odor reduction benefits relative to broadcasting persisted for all methods except aeration infiltration, and odors associated with direct ground injection were not different from the untreated control. Shallow disk injection provided substantial odor reduction with familiar toolbar equipment that is well adapted to regional soil conditions and conservation tillage operations.

Protocols for Reliable Field Olfactometry Odor Evaluations

Specific gasses (odorants) are often poorly correlated with odors, which require human perception. Thus, olfactometry is used to quantify odors, which commonly contain a complex mixture of offensive compounds. Laboratory-based dynamic olfactometry is expensive and time-consuming, and it is accompanied with sample container/ preservation issues. Field olfactometry provides real-time measurements at lower detection levels, but is influenced by environmental factors. This study explores the use of field olfactometry for quantifying dilutions-to-threshold (D/T) of environmental malodors. Nasal Ranger Field Olfactometer (NRO) instruments were used to collect 3096 individual D/T observations at livestock facilities in central Pennsylvania. Twelve to 16 observations were collected at each sampling station using multiple assessors, capturing four concurrent readings each. The multiple-assessor repeat observation (MARO) technique revealed that the reproducibility of D/T observations (across assessors) was more precise than replicate observations by individual assessors (repeatability). Observations were significantly (P<0.0001) influenced by odor source distance, wind direction, barometric pressure, and wind velocity. Power analysis showed that the 16-sample MARO using NRO method achieved 95% odor panel confidence with a power value of 0.90 at lower-D/T (2,4) and upper-D/T (30, 60) levels. Mid-range D/T settings of 7 and 15 exhibited the greatest odor panelist variability. This study shows that MARO field olfactometry can reliably estimate odor D/T differences, even with weather variations. It is noteworthy, however, that the greatest numbers of observations (n= 85-91) are needed at D/T levels of 7 to 15 (to achieve 95% confidence), precisely the range used to define nuisance odor conditions in some states.

Factor Analysis of Downwind Odours from Livestock Farms

Odour emissions from livestock operations in Ontario have raised significant public concerns. In this study, downwind odour measurements were conducted during a 7-week period in July and August in 2004. The study involved taking measurements at two poultry farms, six dairy farms, and six pig farms in southern Ontario using both human assessor observed Nasal Ranger field olfactometers and an electronic nose developed in our research laboratory. The factors considered include animal species, distance to the odour source, and weather conditions (i.e. wind speed, temperature, cloud cover, and atmospheric stability). The collected data were studied and the relationships between individual factors and downwind odour intensity were analysed. In addition, the significance of the factors was investigated and ranked. The results show that downwind livestock farm odour should be considered as a complex system and it is suggested that multi-factor analysis be performed. The ranking of the significance of factors to odour intensity can improve the understanding of downwind odour systems and enhance the efficiency of odour evaluation and reduction techniques. Responses of the gas sensors in the electronic nose were compared with the perceived odour intensities, and good agreement was reported.

Odor Concentrations Downwind of Idaho Dairies and Heifer Facilities

Odor and gas concentrations were sampled on 38 dairies and 15 heifer and calf raising facilities in southern Idaho. Odor detection threshold was measured using a Nasal Ranger field olfactometer, and odor intensity was measured using n-butanol. Gas concentrations for total reduced sulfur (hydrogen sulfide) were measured at each farm's most probable odor source, 50 m downwind, and 200 m downwind using a Jerome meter, and ammonia was measured using Drger diffusion tubes. The type and management of manure handling systems were found to have the greatest impact on odor concentration versus the number of animals on the facility. There were observations of individual facilities within each subject group that emitted odors much less and up to twice the group averages. Flushed freestall and scraped freestall systems were shown to have the greatest measured odor concentrations, while open-lot facilities had lower measured levels. Seasonal variations on each type of dairy studied were found to have a significant impact on odor and gas concentrations at the source. Odor concentrations from heifer facilities were found to be similar to those of open-lot dairies. Porous geotextile covers used on secondary manure separation basins were found to be effective in reducing odor concentrations by half. Odors that were in excess of 15 dilutions to threshold, using the Nasal Ranger, were found to be objectionable when odor panelists were located at a rural residence during 50% of the odor measurements. Panelists observing the same level of odor would have found it objectionable nearly 80% of the time if the odor were detected during a party or event at a rural residence.

Comparison of field olfactometers in a controlled chamber using hydrogen sulfide as the test odorant

A standard method for measuring and quantifying odour in the ambient air utilizes a portable odour detecting and measuring device known as a field olfactometer (US Public Health Service Project Grant A-58-541). The field olfactometer dynamically dilutes the ambient air with carbon-filtered air in distinct ratios known as "Dilutions-to-Threshold" dilution factors (D/Ts), i.e. 2, 4, 7, 15, etc. Thirteen US states and several cities in North America currently utilize field olfactometry as a key component of determining compliance to odour regulations and ordinances. A controlled environmental chamber was utilized, with hydrogen sulfide as the known test odorant. A hydrogen sulfide environment was created in this controlled chamber using an Advanced Calibration Designs, Inc. Cal2000 Hydrogen Sulfide Generator. The hydrogen sulfide concentration inside the chamber was monitored using an Arizona Instruments, Inc. Jerome Model 631 H2S Analyzer. When the environmental chamber reached a desired test concentration, test operators entered the chamber. The dilution-to-threshold odour concentration was measured using a Nasal Ranger Field Olfactometer (St Croix Sensory, Inc.) and a Barnebey Sutcliffe Corp. Scentometer. The actual hydrogen sulfide concentration was also measured at the location in the room where the operators were standing while using the two types of field olfactometers. This paper presents a correlation between dilution-to-threshold values (D/T) and hydrogen sulfide ambient concentration. For example, a D/T of 7 corresponds to ambient H2S concentrations of 5.7-15.6 microg/m3 (4-11 ppbv). During this study, no significant difference was found between results obtained using the Scentometer or the Nasal Ranger (r = 0.82). Also, no significant difference was found between results of multiple Nasal Ranger users (p = 0.309). The field olfactometers yielded hydrogen sulfide thresholds of 0.7-3.0 microg/m3 (0.5-2.0 ppbv). Laboratory olfactometry yielded comparable thresholds of 0.64-1.3 microg/m3 (0.45-0.9 ppbv). These thresholds are consistent with published values.

Evaluation of Field-based Odor Assessment Methods

This study investigates the differences between field-based odor assessment methods that may be used to discriminate odors from livestock and food processing facilities. Field olfactometers have been praised for their low cost ($500 - $1200) and portability but criticized for their lack of control of inhalation rates by different panelists, the discomfort of glass inhalation tubes and the odor fatigue caused by poor nasal sealing or removing the scentometer between samples as compared to laboratory dynamic, triangular forcedchoice olfactometers ($30,000). This study evaluated the variability of responses using these three field olfactometers compared to laboratory olfactometry, as well as field and lab odor intensity. Panel responses using laboratory dynamic, triangular force-choice olfactometry and Nasal Ranger field olfactometers were found to exhibit the least amount of variability across odor sources. Significant differences with poor correlation were found between field and laboratory odor intensity methods. Findings of this study should caution regulators, policy makers and investigators about establishing regulatory thresholds or reporting scientific data based on single odor analysis methods or techniques due to the variability in the performance of odor determination methods across the odorous sites investigated.

Comparison of Field Olfactometers in a Controlled Chamber using Hydrogen Sulfide as the Test Odorant

A standard method for measuring and quantifying odour in the ambient air utilizes a portable odour detecting and measuring device known as a field olfactometer (US Public Health Service Project Grant A-58-541). The field olfactometer dynamically dilutes the ambient air with carbon-filtered air in distinct ratios known as Dilutions-to-Threshold dilution factors (D/Ts), i.e. 2, 4, 7, 15, etc. Thirteen US states and several cities in North America currently utilize field olfactometry as a key component of determining compliance to odour regulations and ordinances. A controlled environmental chamber was utilized, with hydrogen sulfide as the known test odorant. A hydrogen sulfide environment was created in this controlled chamber using an Advanced Calibration Designs, Inc. Cal2000 Hydrogen Sulfide Generator. The hydrogen sulfide concentration inside the chamber was monitored using an Arizona Instruments, Inc. Jerome Model 631 H2S Analyzer. When the environmental chamber reached a desired test concentration, test operators entered the chamber. The dilution-to-threshold odour concentration was measured using a Nasal Ranger Field Olfactometer (St Croix Sensory, Inc.) and a Barnebey Sutcliffe Corp. Scentometer. The actual hydrogen sulfide concentration was also measured at the location in the room where the operators were standing while using the two types of field olfactometers. This paper presents a correlation between dilution-to-threshold values (D/T) and hydrogen sulfide ambient concentration. For example, a D/T of 7 corresponds to ambient H2S concentrations of 5.7-15.6 microg/m3 (4-11 ppbv). During this study, no significant difference was found between results obtained using the Scentometer or the Nasal Ranger (r = 0.82). Also, no significant difference was found between results of multiple Nasal Ranger users (p = 0.309). The field olfactometers yielded hydrogen sulfide thresholds of 0.7-3.0 microg/m3 (0.5-2.0 ppbv). Laboratory olfactometry yielded comparable thresholds of 0.64-1.3 microg/m3 (0.45-0.9 ppbv). These thresholds are consistent with published values.

LAND APPLICATION ODOR CONTROL CASE STUDY

The Western Lake Superior Sanitary District (WLSSD) operates a 40 MGD wastewater treatment plant in Duluth, MN which produces 27,000-29,000 wet tons of cake biosolids annually using a temperature phased anaerobic digestion (TPAD) process followed by dewatering with high solids centrifuges. These biosolids are spread on 1800-1900 acres of agricultural land (80-85%) and mine land reclamation sites (15-20%) annually in a year-round land application program. During the spring of 2003, WLSSD received several comments from farmers expressing that biosolids odors were upsetting neighbors surrounding land application sites. To gain a better understanding of biosolids odors in the field, WLSSD conducted a study during the summer of 2003 to document odor strength, extent and duration at 18 agricultural land application sites. The study was conducted using a Nasal Ranger field olfactometer developed by St. Croix Sensory. Biosolids odor strength at and around land application sites was influenced by a variety of factors, including distance, time, weather conditions, and application method. In order to minimize biosolids odor impacts to the people living around land application sites, WLSSD will develop an odor control and response plan based on the data collected and will continue to track the circumstances surrounding odor complaints.