Tosco Refinery: Monitoring

Note: EPA no longer updates this information, but it may be useful as a reference or resource.

How the Fenceline Monitors Work

The refinery has installed three kinds of monitors: FTIR, UV, and laser. All are "open path monitors" – meaning they measure ambient air pollutants occuring over a 1,000-meter light beam path. Monitors are located along both the north and south fence lines, scanning for 38 air pollutants, including some chemicals defined as hazardous in the Clean Air Act, Section 112. The monitors operate every 5 minutes, 24 hours a day, seven days a week and can generate millions of data points in a year.

	Introduction
	History
	Monitoring
	What's Next

FTIR

The Fourier Transform Infrared monitor (FTIR) can detect, identify, and measure many different gases simultaneously, making initial results viewable at a computer in the refinery within seconds of the readings. To identify different gases, the monitor measures how much energy is absorbed in the infrared spectrum. Such a specific measurement of energy allows for the unique identification -- or "fingerprint" -- of each chemical molecule.

The monitor also measures how much of each gas is present. The greater the absorbance, the higher the concentration in the air. At Tosco, the FTIR instruments continuously scan for 30 chemicals, including MTBE; 1,3, butadiene; benzene; ethyl benzene; methane; ammonia; and formaldehyde. Analysis of the raw data can reveal the presence of 300 additional chemicals.

The FTIR monitor also records raw spectral files that can be reviewed later. If a chemical release occurs, it is possible to go back and look at the FTIR files to see when emissions started appearing and how long the release lasted.

Photo byChristy Shake

UltraViolet

This UV monitor checks for benzene, toluene, xylene, carbon disulfide, and sulfur dioxide. Immediate results from the monitor are viewable at a computer in the refinery, but only concentration data is recorded. The UV monitor does not generate preservable spectral data as the FTIR monitor does.

Laser

The Tunable Diode Laser System (Laser, or TDLS) is set to scan for hydrogen sulfide and ammonia. This type of monitoring also sends results to refinery computers, but only concentration data is recorded. Like the laser, the UV monitor, the laser does not generate preservable spectral data.

Pollutants Monitored

Acetaldehyde	Hydrogen sulfide
Ammonia	Methane
Benzene	Methyl mercaptan
1,3-Butadiene	Methyl tert-butyl ether (MTBE)
Butane	Naphthalene
Carbon disulfide	Nickel carbonyl
Carbon monoxide	Nitrous oxide
Carbonyl sulfide	n-Octane
Chlorodifluoromethane	Ozone
Diethanol Amine	Phenol
Dimethyl sulfide	Phosgene
Ethane	Propane
Ethyl benzene	Sulfur dioxide
Ethylene	Toluene
Formaldehyde	1,1,1-Trichloroethane
Furan	2,2,4-Trimethylpentane
n-Hexane	m-Xylene
Hydrogen chloride	o-Xylene
Hydrogen cyanide	p-Xylene

What's Next >>

Opening photo by Christy Shake