The Single Particle Soot Photometer (SP2)


The only instrument in the world that directly quantifies the black carbon (soot) in individual aerosol particles.






  • Pollution characterization
  • Air quality and visibility
  • Atmospheric and climate research
  • Health effects studies
  • Combustion emissions
  • Biomass burning

Click here for a video of the SP2 being used for ice core sampling.        

The SP2's high sensitivity, fast response, and specificity to elemental carbon make it the premier instrument for characterizing air pollution sources and documenting thin atmospheric layers of contamination. It is also ideal for measuring soot in snow, ice or water and for calibrating other black carbon-measuring instruments like the Aethalometer.


New Features

DMT recently released version D of the SP2. The instrument now features an i7 processor with 8GB RAM. This more powerful computer allows the SP2 to measure much higher particle concentrations. It will not lose particles until particles become coincident. Other new features are listed below.

  • Larger 750 GB hard drive 
  • Universal power supply for easier international campaigns
  • Integrated laser and temperature control for greater reliability
  • Software control of the sample pump
  • Additional housekeeping channels
  • Additional USB ports (six instead of two)
  • Additional RS-232 port (two instead of one)
  • Additional Ethernet port (two instead of one)
  • HDMI monitor port in addition to VGA port




Standard SP2 Software

The SP2 comes with a software program that provides a user-friendly virtual instrument panel for the control, data display, and data logging of the SP2 instrument. For instance, the program enables the user to do the following tasks: 

  • View graphs of incandescence and scattering signals from individual particles
  • View the incandescent particle concentration over the last 30 minutes
  • Monitor parameters like YAG laser power and flow measurements
  • Change the charts and data channels displayed in the software
  • Filter data that is saved to the output file so it includes only specific types of particle events


How it Works

The SP2 uses the high optical power available intra-cavity from an Nd:YAG laser. Light-absorbing particles containing mainly black or elemental carbon absorb energy and are heated to the point of incandescence. The incandescent emission is measured and correlated to the particle’s black carbon mass with the help of black carbon proxies like Aquadag or fullerene soot. 

The SP2 also includes a scattering detector, which detects single-particle light-scattering at 1064 nm. The scattering signal can be used to indicate particle size and the black carbon mixing state at the single-particle level. The scattering detector can also be used to detect non-BC-containing aerosol number and mass concentrations. 

The full scattering and/or incandescence response of each particle is completely digitized for detailed analysis. 



Parameter Specification
Measured Parameters Single-particle laser incandescence
Single-particle light scattering
Auxiliary Parameters Temperature
Derived Parameters BC mass distribution as function of particle diameter
Particle number distribution as a function of particle size
Maximum Data Acquisition Rate 0 – 12,500 particles/cm3 at 120 vccm (0 - 25,000 particles/sec; concentrations can basically increase until particles become coincident)
Particle Size Range Scattering signal: 200 – 430 nm diameter (this range encompasses the accumulation mode of most particles, i.e. range where most mass is found).
Incandescent signal: depends on particle density, but 70 – 500 nm mass-equivalent diameter assuming a black carbon density of 1.8 g/cm3
Aerosol Medium Air, 0 - 40 °C (32 - 104 °F)
Lasers Nd:YAG Laser: 1064 nm, 3 MW/cm2 intracavity circulating power
Pump Laser: 808 nm, 4 W
The pump laser can be controlled either through the SP2 software or through the touch-screen on the SP2 front panel.) 
Sample Flow 30 – 180 volumetric cm3/minute (typically 120)
Flow Control Electronic flow control with a laminar flow element (LFE) and a solenoid valve
Pump Two single-head diaphragm pumps encased in a box
Minimum Black Carbon Detection Limit
  • 10 ng/m3
  • 0.3 fg/particle
Calibration DMT recommends calibrating the SP2 every six months and/or before and after every field campaign.
  • The incandescence measurement is calibrated to black carbon mass using DMA-sized Aquadag, fullerene soot or glassy carbon. (DMA refers to differential mobility analyzer, used to extract particles of a single electrical mobility size from a polydisperse aerosol.)
  • The scattering measurement is calibrated to particle size using monodisperse polystyrene latex (PSL) spheres or DMA-sized ammonium sulfate.

DMT offers free software that automates much of the calibration process. The Probe Analysis Package for Igor (PAPI) assists the user in loading, consolidating, and analyzing calibration data files. 
Routine Maintenance Weekly: 
  • Refreshing or replacing the desiccant in the drying cartridge on the purge line 
  • Conducting PSL size check to monitor laser power

Monthly and around field campaigns:
  • Conducting zero check with high-efficiency filtered air sample

Annually (more frequently for high-BC environments):
  • Checking calibration of the laminar flow element on the sample inlet
Recommended Service      Annual cleaning and calibration at DMT service facility 
Front Panel Display
  • System power switch
  • 2 USB 2.0 ports
  • 1/8 in. Swagelok® sample inlet
  • Laser ON/OFF indicator light 
Rear Panel Connections
  • Keyboard port
  • Mouse port
  • VGA and HDMI monitor ports
  • Ethernet port
  • 2 RS-232 communications ports
  • 4 USB 2.0 ports
  • eSATA port
  • ¼ in. Swagelok® purge line
  • ¼ in. Swagelok® exhaust line
  • Exhaust vents
  • System and pump power connections 
Computer System
  • On-board Intel®Core™ i7 CPU
  • 8 GB RAM
  • 750 GB hard drive for data storage
  • NI PCI-6133 DAQ interface card
  • NI PCI-6259 housekeeping data card
  • User interface via standard keyboard, mouse, and 19” monitor (included)
Software SP2 Executable program written in LabVIEW 
PAPI program written in Igor 
Data Storage Capacity Depends on number of particles; at a concentration of 1,000 #/cm3 and a standard flow rate of 120 volumetric cm3/minute, the SP2 computer has the capacity to store 56 hours of continuous data 
Communications Output Gigabyte Ethernet interfaced through an Intel® PC82573V PCIe GbE controller 
Power Requirements SP2: Universal Voltage
External Pump: 30 W
Dimensions SP2: 48 cm W x 61 cm L x 26 cm H 
Pump: 20 cm W x 25 cm L x 10 cm H
19" Monitor: 37 cm W x 22 cm L x 39 cm H
Weight SP2: 26.1 kg
Pump: 3.4 kg
19" Monitor: 3 kg
Shipping Container Durable Atlas Case Corporation ATA Transit Case that conforms to the Air Transport Association’s Specification 300 Category 1 standards
Environmental Operating Conditions Temperature: 0 – 40°C (32 – 104 °F)
RH: 0 – 100% RH non-condensing

Specifications are subject to change without notice. The SP2 is a Class I Laser Product with U.S. Patent # 5,920,388, exclusively licensed to DMT.


Included Items

  • Instrument with internal data storage
  • Data playback and archiving software
  • Hard-body Shipping Case
  • Operator Manual
  • One-year warranty
  • One day of training at DMT facility

Accessories (Purchased separately)

  • Beam scan camera and software​
  • YAG optics kit (spare YAG crystal and output coupler)
  • Laser alignment bench
  • Nebulizer for liquid samples with optional auto- sampler
  • Aircraft Aerosol Inlet (see picture at right)


SP2 software versions 4.2 and later are compatible with the U5000AT+ Ultrasonic Nebulizer from CETAC Technologies. The nebulizer is ideal for testing black carbon in liquid samples.



How to Order

Contact DMT for pricing or more information.


Phone: +001 303 440 5576
Fax: +001 303 440 1965


Selected Bibliography

Stephens, M., N. Turner, and J. Sandberg, “Particle identification by laser-induced incandescence in a solid-state laser cavity,” Applied Optics, 42 (19), 3726-3736, 2003. Link

Slowik, J. G., E. S. Cross, J. -H. Han, P. Davidovits, T. B. Onasch, J. T. Jayne, L. R. Williams, M. R. Canagaratna, D. R. Worsnop, R. K. Chakrabarty, H. Moosmüller, W. P. Arnott, J. P. Schwarz, R. S. Gao, D. W. Fahey, G. L. Kok, and A. Petzold, “An inter-comparison of instruments measuring black carbon content of soot particles,” Aerosol Science and Technology, 41, 295-314, 2007. (1 Mar 2007)Link

Baumgardner, D., G. L. Kok, and G. B. Raga, “On the diurnal variability of particle properties related to light absorbing carbon in Mexico City,” Atmospheric Chemistry and Physics, 7, 2517-2526, 2007. (14 May 2007)Link

McConnell, J., R. Edwards, G. Kok, M. Flanner, C. Zender, E. Saltzman, J. Banta, D. Pasteris, M. Carter, J. Kahl, “20th-Century Industrial Black Carbon Emissions Altered Arctic Climate Forcing,” Science, 317, 1381-1384, 2007.Link

Moteki, N., Y. Kondo, Y. Miyazaki, N. Takegawa, Y. Komazaki, G. Kurata, T. Shirai, D. R. Blake, T. Miyakawa, and M. Koike, “Evolution of the mixing state of black carbon particles: Aircraft measurements over the western Pacific in March 2004,” Geophysical Research Letters, 34, doi:10.1029/2006GL028943, 2007. Link

Subramanian, R., G. L. Kok, D. Baumgardner, A. Clarke, Y. Shinozuka, T. L. Campos, C. G. Heizer, and B. B. Stephens, “Black carbon over Mexico: the effect of atmospheric transport on mixing state, mass absorption cross-section, and BC/CO ratios,” Atmospheric Chemistry and Physics, 10, 219-237, 2010. (20 October 2009) Link

Bisiaux, M., R. Edwards, A. C. Heyvaert, J. M. Thomas, B. Fitzgerald, R. B. Susfalk, S. G. Schladow, and M. Thaw. “Stormwater and Fire as Sources of Black Carbon Nanoparticles to Lake Tahoe.” Environmental Science & Technology. Feb 2011. Link

Click here for a comprehensive list of SP2-related publications.