Don’t Overlook Total Cost of Ownership
When Purchasing a Gas Monitor
As anyone who owns an inkjet printer knows, the printers themselves are extremely inexpensive. It’s the ongoing cost of ownership — ink cartridge replacement — that can strain the budget.
What you may not know however, is that the majority of hazardous gas monitoring systems also have fairly hefty ongoing costs of ownership. And like those inkjet cartridges, sensor replacement and maintenance can end up putting a significant strain on operational budgets.
In this article, we compare the ongoing costs associated with several different detection technologies with various PureAire detection systems. Hopefully, the information it contains will help you better evaluate competitive bids and make more informed purchasing decisions.
Chemically Impregnated Paper Tapes
The gas detector that most closely mimics the inkjet printer model is the paper tape detection system. Depending on the particular instrument, these gas monitors consume anywhere from one to four tapes a month under normal monitoring conditions. Tape consumption is even greater if the gas being monitored is frequently present.
These chemically impregnated paper tape detection systems are widely used in the semiconductor industry for the monitoring of toxic gases such as arsine, phosphine, chlorine, HF, and other toxic gases. It is not uncommon to find installations where paper tape systems are keeping hundreds of individual monitoring points under surveillance.
Unfortunately, there’s a significant annual cost associated with the paper tape detection technique. Let’s take a look at the ongoing yearly costs associated with monitoring 134 points for both types of systems. The paper tape example assumes the use of a popular four-point detection system.
Paper Tape System
- Number of 4-point systems required: 34
- Recommended tape replacement frequency: Monthly
- Number of replacement tapes
required annually: 408 - Cost per instrument: $1,680
- Total monitoring cost per year: $57,120
PureAire Renewable Electrochemical Sensors
- Number of sensors required: 134
- Recommended sensor recharge frequency:
Every 6 months - Number of replacement sensors required annually: 0
- Electrolyte cost: $5,130
- Membrane cost: $4,050
- Total monitoring cost per year: $9,180
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Disposable Electrochemical Sensors
Gel-type, or disposable, electrochemical sensors are another commonly available technology for toxic and hazardous gas detection. But as with many “disposable” products, this convenience comes at a relatively high cost. As the following example illustrates, replacement cells are not inexpensive and can drive up overall cost of ownership considerably for a monitoring system with even a modest number of points.
Here’s how the annual maintenance costs break down for a 30-point ammonia monitoring system.
Disposable Electrochemical Sensors
- Number of sensors required: 30
- Recommended replacement frequency: Yearly
- Number of replacement sensors required annually: 30
- Cost per replacement sensor: $389
- Total annual cost: $11,670
PureAire Renewable Electrochemical Sensor
- Number of sensors required: 30
- Recommended recharge frequency:
Every six months - Number of replacement sensors required annually: 0
- Electrolyte cost: $1,140
- Membrane cost: $900
- Total monitoring cost per year: $2,040
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Disposable Electrochemical Oxygen Sensors
When monitoring certain gases, such as oxygen deficiency, the difference in overall cost of ownership between disposable sensors and PureAire’s zirconium oxide O2 sensor (see “Zero Maintenance Oxygen Monitor”, back cover) is even more dramatic. The following summarizes the total 5-year cost of ownership for a small, 5-point oxygen deficiency monitoring system.
Disposable O2 Sensor
- Number of sensors required: 5
- Recommended calibration frequency (due to sensor drift): Every 3 months
- Calibration labor cost (per sensor): $200/year (based on $100/hour labor cost)
- Number of replacement sensors required annually: 5
- Sensor replacement cost (per sensor): $165/year
- Total annual cost per sensor: $365
- 5-year cost: $9,125
PureAire Zirconium Oxide Sensor
- Number of sensors required: 5
- Calibration frequency: None required
- Calibration labor cost (per sensor): $0
- Number of replacement sensors required annually: 0
- Consumables cost: $0
- Total annual cost per sensor: $0
- 5-year cost: $0
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As you can see from the preceding examples, gas monitoring systems which may be less expensive to acquire may be significantly more expensive in the long run in terms of labor, consumables, and/or replacement sensors. This is particularly true of large installations involving dozens or even hundreds of monitoring points. In those instances, cost of ownership over a four or five year period may actually exceed the initial purchase price — not an easy expense to swallow when operational budgets are lean and staff in short supply.