GT-321 Handheld Particle Counter

The handheld GT-321 is a portable particle counter that counts particles down to 0.3 microns—giving you portability and reliability at the lowest price in the industry. Don’t let the size fool you—the GT-321 is completely self- contained with its own internal battery and sample pump, and is programmable, allowing you to choose your particle size of interest from five sizes: 0.3, 0.5, 1.0, 2.0, or 5.0 microns. Unlike other counters that can take up to a minute to deliver results, the GT-321 starts delivering volumetric concentration results in about 6 seconds! This facilitates quick multi-site sampling, tracing particle sources and site particle trending.


The GT-321 has a simple operation with only two front-panel buttons control the size channels and sample cycle. The side-mounted power switch allows for convenient thumb operation. The self-contained battery pack powers the unit for 8 hours of typical intermittent operation, and for up to 5 hours of continuous use. The included AC adapter operates the counter, even when the battery pack is discharged, and recharges the depleted battery overnight (16 hours) when turned off. Units are available for same-day or next-day shipping!


  • Most inexpensive counter on the market
  • Simple Operation
  • Fast Sampling
  • Battery or AC Powered
  • Keypad Selectable Sizes


  • Controlled Environments
  • Indoor Air Quality
  • Process Control
  • High resistance values to minimize signal line resistance
  • HVAC Applications
  • Filter Testing
  • Laboratory Environments
  • Manufacturing Environments
  • Emission Sourcing


Operating Principle
Counts individual particles using scattered laser light
Count Channels: 1 (Selectable)
Particle Size Range: 0.3, >0.5, >1.0, >2.0, and >5.0 μm (selectable)
Concentration Range: 0–3,000,000 particles per cubic foot (105,900 particles/L)
Accuracy: ± 10%, to calibration aerosol
Sensitivity: 0.3 μm
Flow Rate: 0.1 cfm (2.83 lpm)
Concentration Limit: 3,000,000 / cf
Sample Time: 1 minute total (first reading in 9 seconds, subsequently
every 6 seconds)
Data Memory: None
Light Source: Laser diode, 30 mW, 780 nm
Power: 6V self-contained battery pack–provides 8 hours of typical intermittent operation, up to 5 hours continuous use
AC Adapter/Charger: AC to DC module, 100–240 VAC to 9 VDC @ 350 mA typical
Communications: RS-232
Certifications: Meets or exceeds CE, ISO, ASTM, and JIS international certifications
Display: 16-character LCD
Keyboard: 2-button membrane
Cont. Operating Time: 5 hours
Recharge Time: 15 hours
Software: No
Power Supply / Charger: Yes
Size: Height = 6.25” (15.9 cm) Width = 3.65” (9.3 cm) Thickness = 2.0” (5.1 cm)
Weight: 1.74 lb – 28 oz (0.79 kg)
Operating Temperature: 0 ̊ C to +50 ̊ C
Storage Temperature: -20 ̊ C to +60 ̊ C
Supplied: Operation Manual Custom Serial Cable AC to DC Converter Module with IEC AC Power Cord Isokinetic Sample Probe Screwdriver Carrying Case Zero Particulate Filter

Specifications are subject to change at any time