Oxygen Deficiency Monitor
Model 221R

Price: $1,870.00

up to 10 units
Orders placed after December 16th will ship on January 3rd.

Pricing shown is for North America only. For other regions, contact your local distributor or AMI for pricing.

Select Your Configuration


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.

Features & Benefits

Model 221R Remote viewModel 221R Close up

Special Safety Features

Rechargeable battery backup with low power alarm, tamper-resistant alarm setpoints to prevent user override, calibrations error detection, and front panel lock-out.


Special Safety Features

The MODEL 221R is certified by a 3rd party testing lab to meets UL 61010-1 Safety Requirements for Electrical Equipment for Measurement, Control, and Laboratory Use.


Washdown-Ready Metal Enclosure

The powder-coated aluminum enclosure of the Analyzer is designed to provide protection against ingress of dust and water from low pressure spray. Design protects analyzers in difficult industrial environments and allows for low pressure washdown of the unit.


Audible Alarms & Relays

Detection of an Oxygen-Deficient environment will trigger a 95 dB alarm to warn of danger. Additionally, includes relays for triggering safety beacons or exhaust fans.

Audible Alarms & Relays

Alarms are preset to oxygen levels mandated by OSHA. Normal ambient atmosphere has an oxygen concentration of 20.9%. The OSHA Respiratory Protection Standard 29 CFR 1910.134 states 19.5 percent oxygen as the level below which an oxygen-deficient atmosphere exists and requires, generally, that all oxygen-deficient atmospheres be considered immediately dangerous to life or health.

10-Year Sensor Life

The Zirconium Oxide Sensor provides up to 10-years of operational life while only requiring simple, periodic calibration. Detection technology is IDEAL for monitoring oxygen safety levels. Maintains accuracy over wide temperature range and not affected by changes in barometric pressure.


10-Year Sensor Life

AMI's zirconium oxide sensors provide the best option for monitoring oxygen levels in inert atmospheres due to their stability, limited maintenance and up to 10 years of service life. Electrochemical O2 sensors require regular calibration and replacement, making them less suitable for oxygen deficiency monitoring.


Optional Remote Probe

Allows monitoring of locations away from the control unit. Comes standard with a 12 ft (3.6m) cable but can be extended by the customer up to 300 ft (91.4m).

Why Choose AMI?

The AMI Model 221R offers the most reliable safety oxygen deficiency monitor to protect your staff. How can you be sure? Keep reading to learn about the AMI difference.

competitor 1
competitor 2

Advanced Micro Instruments 221R

Competitor #1

Competitor #2

Zirconium Oxide

Zirconium Oxide

Zirconium Oxide

Zirconium Oxide based sensors are the best option for Oxygen Deficiency Monitors and commonly used by most major manufacturers including AMI. They offer up to a 10-year service life as well as being incredibly accurate, not affected by sudden swings or drifts in barometric pressure, and require minimal maintenance over the life of the sensor.

Number of Alarms

The AMI Difference




Having only two alarms limits a unit to only measuring for low oxygen levels. The additional of a third alarm allows the 221R to monitor for oxygen-enriched environments, which is recognized by OSHA as a health risk.

Oxygen Enrichment Alarm

The AMI Difference

Oxygen-enriched environments are recognized by OSHA as a health risk. Companies that want to protect employees across the entire spectrum for oxygen safety, from low to high levels, should make this a requirement in their purchase decision. The 221R contains a dedicated oxygen enrichment alarm that triggers at a preset threshold of 23.5%.

Default Alarms Settings

The AMI Difference

Alarm one: 19.5%,
Alarm two: 20.0%, and
Alarm three: 23.5%

Alarm one: 19.5% and
Alarm two: 18.0%

Alarm one: 19.0%,
Alarm two: 17.0%, and
Alarm three: 15.0%

AMI's 221R is designed and configured to power-up and be ready to monitor 'straight out of the box'. It is preset with OSHA's critical thresholds of 19.5% for 'deficient oxygen levels' and 23.5% for 'oxygen-enriched environments'. It also is the only unit that contains a preset warning alarm at 20% to give staff a 'safety buffer' and more time to exit before an environment becomes oxygen-deficient. Other units require set-point adjustments, which can add complexity to the installation and introduce the potential for errors - all of which can have a critical impact on safety.

Adjustable Alarm Set-Points

The AMI Difference

The main purpose of oxygen monitoring is to keep an environment safe for staff with thresholds specified by OSHA. That means monitoring for oxygen at preset thresholds of 19.5% and 23.5% oxygen. If these setpoints are adjustable, it introduces a major RISK for both safety and compliance.

4-20 mA Outputs

The AMI Difference

All Major Oxygen Deficiency Monitoring units include these output signals.

Powder-coated aluminum



Oxygen deficiency monitors are commonly installed and used within industrial and commercial environments. AMI's metal enclosure will provide superior protection to physical abuse that can be common in harsh environments.

Access to Controls

The AMI Difference

Easy access latched, hinged,
lockable protective door

Screw on cover

No protection,
exposed controls

Easy access to the control buttons of an oxygen deficiency monitor is important for calibrating the product. It is also important to protect the controls from damage or accidental tampering. Some solutions have a screw on cover that requires a screw driver to remove. Others provide zero protection for the controls. AMI's 221R has a hinged metal cover with viewing window. It will protect the analyzer controls while still allowing quick access for a technician. It can also be locked, if desired, to protect against tampering.


The AMI Difference

Some facilities must perform washdowns for sanitary compliance. So It is important they select an Oxygen Deficiency Monitor designated as 'Washdown-Ready'. AMI's 221R is engineered for use in a washdown environment. Whereas other deficiency monitors will fail due to sensor or electronics damage from water ingress.

Remote Sensing Capability

The AMI Difference

Most manufacturers offer remote monitoring capability through the purchase and installation of a probe or display unit that becomes wired to the main control unit. But monitoring ranges among manufacturers can differ significantly. Understand a greater range offers greater flexibility, and this is especially true for companies that are constrained by difficult floor plans. The remote probe of the 221R can be installed up to 300 ft away from the main console, offering customers the furthest range in the industry.

Built-in Battery Back-Up

The AMI Difference

Oxygen safety monitoring must operate 24/7. But facilities must always be ready to contend with an unexpected including loss of power. If an Oxygen Deficiency Monitor has no emergency power, staff is at immediate risk in the surrounding areas until power is restored. The 221R includes a built-in battery back-up for this type of situation and ensures no disruptions to your monitoring for safe oxygen levels.

Power Loss Alarm

The AMI Difference

In addition to a battery back-up, it is important to know if power is ever lost to the Oxygen Deficiency Monitor. The 221R contains an audible alarm, and it will trigger if the monitor loses power and the back-up batteries are nearing charge depletion.




The price point of the 221R is extremely compelling when considering all its unique features and advantages not seen on other competitive units.

Technical Specifications

Physical & Eletrical Specifications
4.0 lbs
(1.8 kg)
Wall mountDiffusion screen. No pump, sample tubing or fittings required3-digit LCD (reads full scale from 0.0% to 25.0%)
100 –240 VAC <11 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
  • Gas Calibration Block
COMMAND CENTER SOFTWAREIncluded Software, which provides access to advanced functions:
  • Calibration history
  • Alarm configurations
  • Data Log history of O2 measurements, power history
  • Security settings

Model 221R Downloads