Based on the Sechrist 3500CP-G user manual as of September 2026. Use your unit’s manual as the final authority; this page is a preventive-maintenance checklist, not a service manual.

A used Sechrist 3500CP-G air/oxygen blender is only as trustworthy as its last performance verification. The manufacturer deliberately keeps routine maintenance small ¡ª periodic performance verification, inlet-filter replacement, and exterior cleaning ¡ª while reserving calibration and servicing for Sechrist-trained and authorized personnel. If you maintain, buy, or accept a 3500CP-G, the practical question is simple: which of those tasks were done, when, and who can prove it?

What routine maintenance covers

According to the Sechrist 3500CP-G user manual, routine maintenance of the gas mixer is limited to periodic performance verification, replacement of the inlet filters, and cleaning of exterior surfaces. The manual is explicit about the boundary: a mixer that needs calibration or service must not be used until the necessary procedures are performed and the equipment is tested to confirm it functions properly. Calibration and servicing may only be accomplished by personnel trained and authorized by Sechrist Industries.

That boundary matters for hospital biomed teams. It means your in-house team can own the verification and filter schedule, but a full calibration or internal service event should be documented with the name of the authorized party ¡ª and that record is exactly what you need when accepting a used unit.

Performance verification: before each use and monthly

The manual describes performance verification before each use and a more extensive procedure at least once a month (or more frequently when the facility or clinical situation requires). Before each use, the checks confirm the blender is supplying the mixture you set and behaving normally. The monthly procedure goes further and should be run with the analyzer and setup the manual specifies, then compared against the manual’s pass criteria.

Without quoting the manual’s internal numbers, a meaningful verification record should capture:

• Inlet air and oxygen supply pressures within the range the manual states.
• Delivered oxygen percentage at the settings you use, measured with a calibrated oxygen analyzer.
• Flow behavior at low and high settings, including any hissing, instability, or failure to reach the set value.
• The bleed-control setting, because the 3500CP-G lets you turn the bleed on or off for quieter low-flow operation.

If verification fails, remove the blender from clinical use. Do not keep it in service while waiting for a calibration slot.

Inlet filters and exterior care

Inlet filters should be replaced on the schedule in the manual or your facility’s PM program, and the replacement should be logged. Exterior cleaning follows the manual’s allowed agents and methods; avoid anything that can damage the ABS housing, labels, or gas ports. Visual checks belong in every maintenance event: look for damaged filters, cracked housing, worn fittings, and connectors that no longer seat cleanly.

Calibration and the two-year inspection boundary

Sechrist documentation describes a more thorough inspection of air/oxygen mixers on a longer cycle ¡ª a two-year interval appears in Sechrist material ¡ª followed by recalibration by Sechrist-authorized personnel. Confirm the exact interval and procedure in the English manual for your unit’s version, then treat that event as a hard acceptance requirement for any used blender you buy: a unit that has passed its two-year mark without an authorized inspection has an open maintenance obligation, not a clean record.

Records to request with a used 3500CP-G

If you are mid-purchase, start with the separate walkthrough on verifying a used Sechrist 3500CP-G before you buy, which orders the checks around the unit itself. The checklist here stays on the maintenance-record side: what a clean PM trail looks like for the serial number.

• Serial number matched across every document and the unit label.
• Performance-verification logs with dates and the analyzer used.
• Inlet-filter replacement history.
• Calibration certificate from Sechrist-trained/authorized personnel, with date and due date.
• Notes on any service event and who performed it.

Building a PM record file that survives an audit

A PM record file has one job: to prove, for a specific serial number, that each required task happened at the required time and that any failure was resolved before the unit returned to service. For a 3500CP-G, that file contains verification logs (with the analyzer identification and the values measured), filter-replacement dates, cleaning events, and the authorized calibration certificate. Two habits keep the file useful across handoffs. First, record the failure and its corrective action together; an auditor or a future buyer cares less about a single failed check than about what happened next. Second, keep the file with the device’s asset record so a serial-number search returns the whole history rather than a folder of loose sheets. When you buy a used blender, ask to see that file assembled for the unit’s serial number ¡ª a seller with a clean file can show it in minutes, while a seller without one will offer to “find it later.”

PM and acceptance checklist

Questions PM teams ask

Can hospital biomed calibrate the 3500CP-G?

Not without Sechrist training and authorization, per the manual. Your team performs verification, filter changes, and cleaning; calibration and service stay with authorized personnel.

What if the monthly verification fails?

Remove the unit from clinical use immediately and arrange authorized calibration or service. Document the failure and the corrective action before returning the unit to service.

Does a “tested” label on a used unit replace the calibration record?

No. “Tested” without a dated performance-verification log and an authorized calibration certificate does not tell you who did what. Ask for the records that match the serial number.

A 3500CP-G with a clean PM trail is a dependable piece of capital. One with gaps in its verification or calibration history is a negotiation point, not a finished deal. If you are evaluating a used blender, view HHG’s Sechrist 3500CP-G product page and request the serial-matched maintenance records before you decide.