Wind direction, speed and temperature are measured using a hand-held Kestrel 1000 meter, and the cloudiness and weather are noted. More sophistical meteorological data has been used to calculate the back-trajectory of odor plumes using data from the National Weather Service in MesoWest plus the HYSPLIT dispersion model. Odor investigation data is captured in an in-house database that is rather old and does not allow for easy queries. Since 2010, the number of odor complaints per year has risen from around 3,400 to 7,500, decreasing in 2017 to 6,000 . Odor complaints are received by phone or via their website, which is also available through their app.No electronic nose technology is currently used although a report surveyed dozens of emerging technologies . The authors noted that e-noses were primarily used for quality control for food and other products, and that a large effort would be required for field tests for environmental odor detection. Two major case studies from SCAQMD are informative. The first case is metallic odors in the industrialized section of the City of Paramount that began in 2013 . Nickel and hexavalent chromium were detected in air samples. Three businesses with metal-related operations were identified and many community meetings were held to address both odor and air toxics concerns. Under an Order for Abatement, one company was required to take measures to reduce odors in July 2017. They improved air pollution controls in their grinding room and made other improvements, and the number of odor complaints decreased. The second case is the coastal area of Seal Beach, Huntington Beach, and Long Beach that experienced “gas/sulfur/chemical” odors . To help find the allusive source, sampling was performed between March 2017 and October 2018 in partnership with local fire departments. SUMMA canisters were analyzed for the presence of volatile organic compounds,vertical farming equipment suppliers and samples collected in Tedlar™ bags were analyzed for total reduced sulfur compounds.
Crude oil was the likely source of the compounds detected, and in October 2018 a violation was issued to an oil tanker that, upon inspection, had 7 out of 10 pressure release devices leaking . Portable hydrocarbon-sensing devices and gas imaging cameras were used to detect the leaks. Monitoring for other sources using a forward-looking infrared camera and further sample collection are ongoing. To address the beach communities’ health concerns from the intermittent exposures, and to put the monitoring data into context, a “frequently asked questions” document was created . The conclusions were that the levels of hydrogen sulfide were below the 30 ppb one-hour state standard, the levels of specific hydrocarbons were below their acute limits, and that cancer risk was not at a level of concern due to the intermittent nature of the exposures.The Bay Area Air Quality Management District , headquartered in San Francisco, sets an odor limit of 5 dilutions-to-threshold at or beyond the facility fenceline, which is applied after at least 10 complaints are received within a 90-day period . Further investigation is required if a further 5 complaints are received within the next 90 days. Interviews with staff provided recent information and insights into investigation techniques currently used. Although still found in their local regulations, the use of odor panels to evaluate samples captured in bags ended over five years ago. The primary concern was that employees, who served as the panelists, were worried about exposures to unknown compounds and experienced negative sensations. Using air monitoring results for specific odorants and comparing the concentrations to odor detection threshold concentration was considered not in line with odor being a sensory nuisance . Lacking any quantifiable sensory method, air inspectors now conduct source-by-source investigations using their own sense of smell with moderate success. An inspection is triggered when 5 or more independent complaints are received and can result in a Violation Notice. Although their “Odor Policies and Procedures” is currently being revised, BAAQMD has several experiences worth sharing.
When an odor complaint is received during office hours, within 15 minutes it is assigned to an air inspector who has 30 minutes to contact the complainant. They then meet, experience the smell together and walk toward the source together. No sensory descriptors or training are used. They also explore upwind. If the odor is verified, the source is contacted and, if needed, inspected to see if in violation of the permit. Prior attempts to use field olfactometry offered no advantages to the above method. A database developed in-house manages the case load. Regarding odor management plans that facilities have submitted, the air inspectors found substantial difficulties. Such plans are difficult to enforce, different for each site, written by a third party , and require large amounts of staff review time. Regardless, they are commonly found at WWTPs and trash transfer stations. A prior contract with Envirosuite Inc. was not continued due to the substantial requirements for meteorological data. The project tried to use advanced backtracking technology, based on real-time fine-scale meteorological modelling, to instantly plot and visualize the trajectory of an odor complaint, thereby identifying its likely cause. A current challenge is the overlapping odors found in Milpitas, which have resulted in thousands of complaints. To fingerprint and identify which sources are contributing to the ongoing odors, BAAQMD issued in March 2019 a request for proposals . A community group that meets quarterly is conducting a parallel study. Another challenge is the increase in composting operations, which are often malodorous. Finally, an emerging area of concern is cannabis cultivation, particularly within and around Santa Rosa, California. To understand the operations, BAAQMD staff toured a cannabis cultivation facility and will visit again.To become a “verified complaint,” air inspectors from the Sacramento Municipal Air Quality District rely on the definition of nuisance being about the complainant’s perception and try to verify that. Upon meeting the complainant, the air inspector logs their own description of the odor and sees if it matches that of the complainant. Standardized smell vocabulary would be useful. A verified odor nuisance can lead to a Notice of Violation, which in turn can lead to an Abatement Order that shuts down the facility. The owner must then sue to re open the facility. SMAQMD is considering trying a field olfactometer like neighboring air districts have. Previous tests conducted at the source of an odor need to be translated to fenceline concentrations experienced by the neighborhood.
A current challenge is a rendering facility. California law, the Right-to-Farm Act, exempts such facilities from nuisance law, however. Another challenge is a sweet potato drying operation that has rotting odors. Also, the Zero Waste initiatives are sending more scraps to compost facilities, which are exempt from air regulations, so solid waste programs handle the complaints . Even pleasant aromas can become nuisance odors. A blueberry smell from a food factory was intense enough to trigger migraines. Masking has been done using cherry “perfume” at a solid waste landfill. Complaints are logged into a database that contains over 13,000 records since 1996. The data was transitioned from MS Access to MS Sharepoint, which sends automated e-mails and allows for logging from the field. Responses to questions were received by e-mail from the Feather River Air Quality Management District . Nuisance odor complaints are infrequent and primarily regarding agricultural operations, which are exempt from investigation. For other sources, air inspectors gather from the complainant the type of odor, location, wind direction, topography and any adverse effects experienced. All complaints are investigated, and the air inspectors rely on their own sense of smell and best judgment to trace the odor to the source. The source usually acts immediately to mitigate the problem.Air inspectors from Placer County Air Quality Management District respond to all odor complainants. They drive to the complainant and try to verify the odor, even if they need to wait for an intermittent odor. If detected,grow light shelves they then try to identify the source. No cases have ended up in court, just resolved by mutual settlement. Past experience with a field olfactometer was not helpful due to the transient nature of most odors. The major source of odor complaints is a landfill. The dispersion modelling was not helpful, and sampling was sent for odor intensity testing by a panel. A spray coating did not stop the odor, nor did a cherry/citrus mist at the perimeter. The latter actually magnified the odor. Another nearby source, bioenergy wood piles, was blamed for the odors by the landfill.The San Joaquin Valley Air Quality Management District covers eight counties. Once a complaint is received, the air inspector visits the complainant to determine the type of odor, time of day and GPS location. Driving around, the source is identified. If the source is a permitted facility, the air inspector goes on-site to review the permit and inquire about any upsets or disruptions. If not permitted, the air inspector talks with the source and offers compliance assistance and education. The air inspector always circles back to the complainant to communicate the findings. A senior air inspector often accompanies a new inspector to provide mentoring. Once source of odor complaints was from residents who disagreed with urban planning decisions. Other complaints were from a WWTP that had a pond go anaerobic and a rendering plant, which is now closed. Their database could serve as a model for other air districts. It was developed in-house, which was expensive, but the functionality is impressive. The database is on-line, smart phone friendly, interfaces with their app and, thus, can collect photos and videos. The system sends automated notifications to inspectors by text or e-mail.
It also includes mapping features.Three odor experts in the Colorado were interviewed by phone. Adam Wozniak, an odor expert in the stationary sources program, provided an overview of Colorado’s approaches to nuisance odor investigation. Colorado has the same number of stationary air pollution sources as California, yet a much smaller population. A recent case was odors from a bio-fuel operator north of Denver, which required community meetings. A study of odor’s impact on wellbeing in North Denver has been published . Colorado has 25 odor inspectors at the state level. Most complaints, however, are delegated to the local officers. Both state and local air inspectors are certified annually on how to conduct sensory investigations through a class offered every other month. Odor inspectors are trained to avoid the use of odor notes and instead focus on “detectability,” which is a faint sense that an odor is present, rather than “recognition,” which is a clear sense that an odor is present and can be described. Inspectors’ ability to detect odor intensity, on a scale of 0 to 10, is tested using a “detectability rating test” , and those with extreme senses of smell are disqualified from odor inspections. The Colorado odor regulation from the 1970s, Regulation 2, is a bit of a curse. Regulation 2 codifies field olfactometry dilution-to-threshold limits that are violations when exceeded, namely 2:1 for hog odors, 7:1 for residential/commercial odors, and 15:1 for other land uses . Regulation 2 is a problem because the public complains of odors well below these limits, generally around 2:1 or 3:1. Regardless, to comply with the regulation, field olfactometers are used, primarily the Nasal Ranger® because the more affordable Scentometer is no longer manufactured. The Nasal Ranger® has been customized to meet the dilutions required for Colorado . Persistent complaints receive a 10-day evaluation with follow-up 14 to 30 days later. The evaluation includes mapping of odor frequency, wind direction, and upwind locations. Due to the relatively high D/T limits, few violations occur, and none have ended up in litigation. More commonly, the public is upset with the agency that no violation was triggered. All complaints are tracked in CACTIS software, as is all inspection work. William Brennan at Denver Public Health and Environment was also interviewed by phone. Legal adult use of cannabis began in Colorado in 2014, and today over 350 cannabis cultivation facilities are found within the city limits of Denver. A sharp increase in odor complaints accompanied the rapid growth. Some were probably from disgruntled voters who opposed the legalization. An advisory work group was formed to tackle the issue and included a variety of stakeholders that attended 10 meetings. New odor regulations were developed that now require cannabis growers, edibles manufacturers, and a few other industries to submit Odor Management Plans. An outline is provided as well as example plans.