CAPS NO2 Monitor

The CAPS NO2 monitor provides a direct absorption measurement of nitrogen dioxide at 450 nm in the blue region of the electromagnetic spectrum. Unlike standard chemiluminescence-based monitors, these instruments require no conversion of NO2 to another species and thus are not sensitive to other nitro-containing species. Levels of detection (3σ noise levels) of less than 100 parts per trillion with a 10 second sampling period can readily be attained; a fast response version which offers 1 second time response at reduced levels of detection (1ppb) is also available. These instruments offer completely linear response at concentrations up to several parts-per-million of NO2; this limitation at high concentrations is purely one of optical opacity. This monitor can be rack mounted and requires only a source of NO2-free air for periodic (minutes to hours) baseline measurements. The standard gas flow is 0.85 lpm but lower flow rates with reduced time response can be chosen without loss of sensitivity. Twelve months of on-board data storage (at a 10 second sampling rate) is standard.

If U.S. EPA FEM-certified instruments using the CAPS technology are required, please contact us for a list of suppliers.

  • Visible (450 nm) absorption measurement using patented Cavity Attenuated Phase Shift (CAPS) technology.
  • Measurement of ambient concentrations to 3000 ppbv.
  • Stack Gas Monitoring.
  • Medical Inhalant Purity Monitoring.
  • Combustion Plume Analysis (Fast Response [1 s] Version).
  • LOD (3σ, 10 s) = <0.1 ppb.
  • Direct measurement of analyte – no chemical conversion required.
  • Insensitive to presence of varying levels of nitric oxide, aerosols, humidity and other trace atmospheric species.
  • Essentially interference-free.
  • Linear Response (0-3000 ppbv).
  • Minimal maintenance (periodic change of particle filter).
  • No Toxic Gas Emissions.

Sensitivity (S/N = 3) Ambient Monitoring: < 0.1pppb (10s) Fast Response Version: < 1.5pppb (1s) (No Dryer)
Response Time(10-90%)Ambient Monitoring: 8s Fast Response Monitor: 1s
Sample Flow0.85 | min-1 ambient monitor 4.5 | min-1 fast response monitor
Operating Pressure Ambient
Materials Exposed to Analyte Stainless Steel, PFA and Naflon
Data OutputRS-232 (Data acquisition and instrument control software provided), On-Board Data Storage (6 GB)- Download through USB Port, Front Panel Display
Size/WeightRack mount 19 x 24 x 9.06″, 25lbs. [61x43x23cm, 12kg]
Electric Power100W; 100-250 VAC (50-60Hz)

A Practical Alternative to Chemiluminescence Detection of Nitrogen Dioxide: Cavity Attenuated Phase Shift Spectroscopy, P.L. Kebabian, E.C. Wood, S.C. Herndon, A. Freedman, Environ. Sci. Technol., 42, 6040-6045, 2008.

System and method for trace species detection using cavity attenuated phase shift spectroscopy with an incoherent
light source, P.L. Kebabian, A. Freedman, U.S. Patent No. 7301639 (issued November 27, 2007).

Detection of Nitrogen Dioxide by Cavity Attenuated Phase Shift Spectroscopy, P. L. Kebabian, S. C. Herndon, A. Freedman, Anal. Chem., 77, 724-728, 2005.