OHD: Your Protection Our Priority; OHD, specializes in Occupational Health instruments to help protect your employee’s health & manage your occupational risks. Whether you are looking for the Quantifit Respirator Fit Tester Controlled Negative Pressure Technology, Noise Dosimeters, Sound Level Meters, Environmental Noise Monitoring System, Spirometers, or Audiometers we can provide you with a complete solution, Measurement Instruments, Sound Level Meters, Industrial Analyzers, Industrial Measuring ...