Model 221R

for 10 units or less

Price: $1,730.00

Select Your Accessories


The AMI MODEL 221R is the gold standard for oxygen deficiency & confined space oxygen monitoring. It is used by the thousands in US Government Laboratories, Space Agencies, Universities and a broad range of industries to ensure the safety of personnel. The MODEL 221R provides an incredibly accurate and stable reading over a wide temperature range (0-130°F) and is not affected by changes in barometric pressure. This analyzer is virtually maintenance-free with its unique oxygen sensor delivering a 10-year life expectancy.

Note that the MODEL 221R should not be used in areas where Flammable Gases may be present.

Technical Specifications

Physical & Eletrical Specifications
4.0 lbs
(1.8 kg)
Wall mountDiffusion screen. No pump, sample tubing or fittings required4-digit LCD (reads full scale from 0.0% to 25.0%)
100 –240 VAC <115 Watts.
Battery back-up provides 1 hour of power
4 – 20 mA isolated output signal
Bi-directional RS485 communication
model-221r dimensions
2-year warranty for Parts & Labor for any defects in materials or workmanship. 2-year Warranty for zirconium oxide sensors.
Operational Specifications
Method of Measurement
0 –25.0%+14°F to +122°F
(-10°C to +50°C)
Zirconium Oxide Sensor
(10-year life expectancy)
Monitor Performance Specifications
Minimum detection limit90% UPSCALE RESPONSE TIMES
REPEATABILITYDiurnal Temperature SpecificationAPPROVALS
0.05% of Oxygen<12 sec for
0.0% – 25.0%
±0.1% of range or ±0.1% of oxygen whichever is greater<±1% of scale over temperature rangeUL 61010-1 for Safety Electrical Equipment
CE Marked, Designed to Meet IP65
Analyzer Key Features
OSHA Preset Standard Alarms
  • Below 19.5% Oxygen Danger Level — Red warning light, 95 dB audible alarm, Relay 2 de-energized
  • Above 23.5% Oxygen Enriched Level — Red warning light, 95 dB audible alarm, Relay 1 & 2 de-energized
Additional Preset Alarm
  • Below 20.0% Oxygen Caution Level — Yellow caution light, Relay 1 de-energized
WASH DOWN READYDesigned to withstand direct water spray
  • 1-hour rechargeable battery back-up
  • Tamper-resistant alarm setpoints
  • Front panel lock-out
  • Calibration error detection and alarm
  • Remote Sensing Probe for monitoring up to 300 ft from control unit
  • Pre-wired Type B wall plug
COMMAND CENTER SOFTWAREIncluded Software, which provides access to advanced functions:
  • Calibration history
  • Alarm configurations
  • Data Log history of O2 measurements, power history
  • Security settings

Features & Benefits

Oxygen Deficiency Monitor in Work Environment
MODEL 221R Oxygen Deficiency Monitor installed in area with several gas cylinders

Designed for OSHA Compliance

The MODEL 221R is optimized for safety. Our standard offering provides (3) OSHA-compliant preset alarm relay contacts and a single 95 decibel audible alarm. The “Caution” alarm is preset for 20.0% oxygen, Danger for 19.5% and the Enriched Oxygen alarm for 23.5%. Both the 19.5% Danger and 23.5% Enriched Oxygen condition trigger alarm relay contacts and the 95dB audible alarm to alert personnel of the potentially dangerous situation. This Analyzer is also NRTL-certified to be compliant with UL61010-1, covering safety requirements of equipment for measurement, control and laboratory use.

Image of zirconium oxide sensor
Zirconium Oxide Sensor

10-Year Zirconium Oxide Sensor Technology

AMI’s zirconium oxide sensors are virtually maintenance-free, extremely accurate and stable over a wide temperature range without suffering from changes in barometric pressure. This unique sensor is the perfect choice for reliably measuring percent levels of oxygen in confined spaces, tank storage area, or in the workspace, ensuring personal safety. AMI’s zirconium sensor in the MODEL 221R will last up to 10 years without ever needing replacement.

Zirconium Oxide Sensors
MODEL 221r Oxygen Deficiency Monitor with optional remote probe
MODEL 221R Oxygen Deficiency Monitor with optional remote probe

Optional Remote Probe

The MODEL 221R is available with an optional remote probe for continuous monitoring of locations separate from the control unit. This makes it an ideal solution for making sure difficult to access locations continue to have a safe oxygen level. The remote probe comes standard with a 12 ft (3.6m) cable, but they can be extended by the customer up to 300 ft (91.4m). The probe features the same long-life zirconium oxide sensor as the standard MODEL 221R.

Command Center Software running on laptop connected to oxygen analyzer


The MODEL 221R comes standard with a 4-20mA isolated output signal and bi-directional RS485 communication. It has built-in safety features including rechargeable battery backup and tamper resistant alarms to prevent user override of safety setpoints. It also offers advanced features that can be accessed through AMI’s COMMAND CENTER Software. These includes automatic data logging that provides detailed time-stamped records of O2 measurement, and power supply voltage, as well as calibration history.

Available Accessories

Model 221R Downloads