Indoor Air Quality


Often indoor air quality can be worse than outdoor air quality. This can happen because of malfunctioning appliances like wood stoves, furnaces and hot water heaters or because water infiltration has allowed mold to grow.

To address community needs regarding indoor air quality monitoring, the Bishop Tribe’s Air Program continues to develop its capability in this area. Current sampling/monitoring capacity includes:


The instruments used are shown on this page. These instruments are portable/handheld and quiet. Occasionally, they are left to collect data in an indoor location for 24-hours. The go-to instrument is the GrayWolf DirectSense IAQ probe, which collects a log of data that can be analyzed on-site or later to compare with other data using the Wolfsense software.

directsense probegraphs


Carbon Monoxide

Carbon monoxide is perhaps the most dangerous indoor pollutant. This invisible, odorless gas can be toxic at high concentrations. It is a product of combustion and can be generated from malfunctioning wood stoves, hot water heaters or furnaces.

Tribal members who believe that they may have malfunctioning wood burning or gas-fired appliances are encouraged to buy a high-quality CO detector alarm for their homes and operate according to the instructions provided, and seek advice from the retailer or manufacturer if needed. Residents can also contact their stove retailer or manufacturer, or contact the Air Office for best burning practices with wood stoves, as proper installation and efficient use can lead to a reduction in indoor CO pollution.

Pictured below is an example of a CO detector for homes, that alarms if concentrations exceed safe limits. IMPORTANT: CO detector sensors expire in roughly 5 years and need to be replaced. They can be used in conjunction with the Tribe's DirectSense IAQ probe.

CO alarm


Carbon Dioxide

Like carbon monoxide, carbon dioxide is a colorless, odorless gas. However, it is not considered toxic. It is a product of combustion and of respiration (breathing). Carbon dioxide readings, along with air flow readings, are used to determine if a building or room is adequately ventilated. The instrument below is an example passive monitor that collects information on gas flow past a sensor. It can be used to provide a real time digital display or can be connected to a data logger for a longer period of observation. We can also get this measurement with the DirectSense IAQ probe.

telaire monitor


Temperature & Humidity

Temperature and relative humidity are typically collected as an adjunct to other measures to help complete the picture of conditions. A dedicated thermo-hygrometer or the DirectSense IAQ probe can be used for these measurements.



Radon sampling is conducted with a Durridge Rad7 continuous radon sampler. Most regularly used is the EPA 2-Day test protocol programmed into the instrument. Radon sampling is not a frequent indoor air activity but has been conducted periodically on the reservation since 2006.

photo of radon detector in an office


Particulate Matter

Particulate matter pollution consists of very small particles that may become lodged in the human lung and that can exacerbate a variety of health problems, especially cardiac and respiratory conditions. The two most common sources of particulate matter on the Bishop Reservation are dust and smoke. In indoor settings, malfunctioning wood stoves are the primary source of concern. The instrument below collects information on particulate matter by drawing it through an insert that selects particles that fall below a size cut off (called aerodynamic diameter), it then measures the concentration using light-scattering methods.

photo of particulates sampler on a table


Carbon (Soot)

Soot is composed of hydrocarbon based (aka black carbon) and aromatic (organic) carbon compounds, products of incomplete combustion. Concentrations can be measured using an aethalometer, which measures the light-absorption of particles, and calculates an equivalent concentration. The Tribe's model is the Aeth Labs MA200 (microaethalometer). This sampler is designed to distinguish estimates of heavier hydrocarbon sool from vehicles, and carbon from biomass burning. The sampler is portable, and can be operated in a variety of environments, outdoors and indoors.

sampler running sampler being calibrated


Common Allergens

Sampling indoors for aerosols that include a variety of common allergens is unlike the other monitoring described on these pages, as it involves expensive outside laboratory analyses and is used only in special circumstances. Typically, a build up of indoor allergens is a by-product of an issue with the building itself, or how it is used and maintained. Unlike ambient (outdoor) monitoring results, indoor monitoring results rarely are compared to an official standard, but are compared to a pool of results using similar testing methods.