Environmental odors: What's that smell?

Odors in the environment can come from many sources, including human activities, animals, nature, vehicles, and industrial activities. Click here for a link to the Centers for Disease Control website of various odors/vapors in the environment and what they smell like.

Vapors Sources

Gases or vapors generated by the tank waste accumulate in the tank headspace (area between the waste surface and the tank dome). From time to time, chemical vapors may potentially enter a worker's breathing zone.

Static operations

Hanford’s waste tanks are vented to the atmosphere through pipes that extend above ground from the tank dome.  Double-shell tanks are actively ventilated with exhaust systems. Single-shell tanks are passively ventilated, allowing the tanks to “breathe” with changes in atmospheric pressure, temperature differences between the inside of the tank and the surrounding atmosphere, and wind.

Active operations

In addition, much of the work at tank farms consists of “waste-disturbing activities,” potentially resulting in a greater possibility to stir up vapors that may vent to the atmosphere. During work planning additional controls are put in place to protect workers and their health against potential hazards.

Leading indicators

This is a summary of the PNNL-25533 Leading Indicators Process Development report, developed to provide an overview to inform and educate the reader of the report contents and a list of frequently asked questions on the subject matter.

Tank farm vapors are a mix of gases, and some gases in the mix are more easily detected than others. The more easily detected gases can be monitored by Industrial Hygiene technicians in real-time using handheld instruments. Monitoring for one or two chemicals (a leading indicator also referenced as a limiting chemical) can indicate the presence of other chemicals that cannot be monitored in real-time. It is possible to protect against potentially harmful tank vapors by monitoring for leading indicators. A recent study, (PNNL-25533), concluded that two tank farm gases, ammonia and nitrous oxide, were the best candidates to use as leading indicators. The analysis will be updated next year after more data is collected.

Stack Install Process


Gases slowly move (diffuse) through the waste and into the tank airspace (headspace) [...]Read More


Gases and vapors that accumulate in tank headspaces are released to the atmosphere to prevent [...] Read More


Hanford is home to 177 underground waste storage tanks: 149 single-shell tanks and 28 double-shell tanks located [...] Read More

Waste Transfers

DST to DST waste transfer activities are comprised of DST to DST transfers, DST waste recirculation’s and [...] Read More