Ambient Air Quality

To protect the health of reservation residents, air quality is monitored on the Bishop Paiute Reservation. You can obtain current air quality conditions and web cam image using the "Monitoring" tab above. You can also view other local and regional data portals by clicking on the "Resources" tab.

The Tribe operates 3 air quality monitors, all of which receive 3rd party audits annually. Two instruments are used to measure the concentration of very small particles that are suspended in the air (particulate matter). These measurements are important because the particles are small enough to lodge in the human lung and cause or aggravate health problems. In the Owens Valley, particulate matter is the primary air pollutant and there are two primary sources, dust and smoke.

The Tribe collects measurements for two particle sizes. PM10 refers to particles that are less than 10 microns in diameter (about 8 will fit in the diameter of a human hair). PM2.5 refers to particles that are less than 2.5 microns in diameter. Generally speaking, high PM-10 measurements reflect dust events and high PM2.5 measurements reflect smoke events.

Particulate matter is measured in micrograms per cubic meter of air. Standards have been established by the US Environmental Protection Agency (US EPA) and by the State of California. When the concentration of particulate matter exceeds these standards, health can be adversely affected. All standards refer to the average concentration in a 24-hour period. The Bishop Tribe's standards are the same as the California standards for both particle size.
PM10:  Federal: 24-hour average concentrations must not exceed 150 micrograms per cubic meter
            California: 24-hour average concentrations must not exceed 50 micrograms per cubic meter
PM2.5: Federal: 24-hour average concentrations must not exceed 35 micrograms per cubic meter
            California: Default to federal standard

The Tribe also operates a continuous monitoring system for ground-level ozone. Ozone exists in the Owens Valley largely due to wind transport from more densely poulated areas and major traffic corridors. Additionally, there is some evidence that ozone concentrations increase locally in association with wildfires. More rarely, stratospheric intrusion occurrs and spikes ozone levels briefly. Currently, the Tribe's 1-hour and 8-hour ozone standards are .09 ppm and .07 ppm, respectively. All monitoring systems are all federally approved and use certified instruments, and are audited annually. 

Particulate Monitoring Equipment

The instruments used are a 1405 TEOM for FEM PM10, and a T640 light spectroscopy monitor for FEM PM2.5. These are EPA certified, sophisticated and extremely accurate monitoring devices. They measure the concentration of particulates in micrograms per cubic meter of air. A microgram is one-millionth of a gram. There are over 28 million micrograms in an ounce.

The TEOM operates on a simple principle. Particles are selected for size and drawn into the instrument in a temperature-controlled column. They are deposited on a filter that sits at the top of a quartz element (the weighing device). This element oscillates at a known frequency. As material accumulates on the filter, the frequency of oscillation is changed in a way that is directly proportionate to the mass of particulate. This frequency is measured every 2 seconds along with the flow of air through the instrument and is used to calculate the mass of particles that are in the volume of air, as instantaneous, 1-hr, 8-hr, and 24-hr average concentration values, measured in micrograms per cubic meter.

Air enters the monitor through an inlet (a cyclone or separator) that uses properties of the flow of air to allow only particles that are less than 10 microns to enter the instrument.

The instrument has 3 main components:

• The pump pulls the air through the inlet into the instrument
• The control electronics regulate the volume of air flowing through the unit and ensures proper instrument operation
• The weighing unit measures the mass of particles that are drawn through the unit and deposited on a filter

TEOM TEOM filters

The T640 measures particles by light spectroscopy, where particles of different sizes scatter LED sourced light in measureable quantities of intensity. The particles enter in the sample stream of air pumped in at a low volumetric flow through a conditioner into the instrument. The monitor can also measure different size particles, i.e. PM10, PM10-PM2.5, (though modifications are required to do this for FEM criteria).

PM2.5 monitor monitor inlet

To ensure accuracy of measurements, flow of the air through the instruments, ambient measurements, range, and other criteria are precisely controlled and verified. More information is available via the "Quality Assurance" tab above.


Ozone Monitoring Equipment

The Tribe uses one instrument to measure ozone. It measures the concentrations of a gas composed of three oxygen molecules (O3). Ground-level ozone is a respiratory irritant that may aggravate a variety of respiratory problems, including asthma.

Ozone is measured using a Thermo 49i. This instrument samples the air and determines the amount of ozone using ultraviolet photometry. Ozone is measured in parts per billion (ppb).

The instrument operates on the principle that ozone molecules absorb ultraviolet light at a known wavelength of 254 nanometers and the degree to which ozone is absorved is directly related to the ozone concentration according to a mathematical formula, known as the Beer-Lambert Law.

A small pump draws air through an inlet on the roof of the EMO building. The sample stream is then spit into a reference stream that passes through an ozone scrubber and a sample stream. Solenoid valves allow the two streams between two cells. The UV light intensities in each cell are then measured and the streams are switched. The analyzer outputs the average concentration on the front panel of the instrument and data are also transmitted to the data logger and subsequently to the internet.

The analyzer is challenged biweekly with zero and span and multipoint calibration gases, generated by a dedicated calibration instrument. The monitoring system uses a Teledyne 703E calibrator. More information is available via the "Quality Assurance" tab above.


inlet analyzer ozone racked



Data Transmission

Data are transmitted using special equipment and software developed by Sutron (formerly IPS MeteoStar). The instruments are connected by cable to a Sutron data logger that stores the measurements every second and calculates 5 minute averages. Specialized software polls the data logger every 15 minutes, and transmits this information to web pages which are available to the public.

The DAS also controls automatic ozone QC checks via a gas calibrator connected to the ozone monitor. The DAS programming runs a calibration sequence that performs nightly span/zero checks and biweekly multipoint spans, and also analyzes the test results and automatically qualifies data based on the results.


Sutron logger