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Thermo Scientific Midi 40 CO₂ Incubator
The Thermo Scientific Midi 40 CO₂ Incubator is a compact benchtop cell culture incubator designed for laboratories that need reliable temperature, CO₂, and humidity control without the footprint of a full-size incubator. With a 39.6 L (1.4 cu. ft.) stainless steel chamber, the Midi 40 is particularly well suited for laboratories with modest culture volumes, dedicated research applications, or limited bench space.
Available used and refurbished from American Instrument Exchange, the Thermo Midi 40 provides a practical alternative to purchasing a larger CO₂ incubator when chamber capacity requirements are relatively small. Its combination of a 0–20% CO₂ range, temperature control from 5°C above ambient to 60°C, high-humidity operation, and four adjustable shelves makes it a versatile choice for routine mammalian cell culture and other controlled-atmosphere laboratory applications.
Key Features
Compact benchtop design with 39.6 L (1.4 cu. ft.) chamber
Temperature range from 5°C above ambient to 60°C
0–20% CO₂ control range with thermal conductivity sensor
Temperature control accuracy of ±0.1°C
Temperature uniformity of ±0.5°C at 37°C
Up to 95% relative humidity at 37°C using a removable humidity pan
Type 304 mirror-finish stainless steel interior
Four perforated stainless steel shelves
Programmable high/low temperature and CO₂ alarms
0.3-micron antimicrobial filtration of incoming CO₂
Professionally inspected and tested by American Instrument Exchange
90-day warranty included
Thermo Scientific Midi 40 CO₂ Incubator Overview
The Thermo Scientific Midi 40 fills an important niche between very small specialty incubators and conventional full-size CO₂ incubators. Its compact dimensions allow it to fit comfortably on a laboratory bench while still providing four shelves and enough usable chamber space for routine cell culture work.
Temperature can be controlled from 5°C above ambient to 60°C, with ±0.1°C control accuracy and ±0.5°C uniformity at 37°C. CO₂ concentration is adjustable from 0–20%, with a thermal conductivity sensor continuously monitoring chamber conditions. The system is designed to restore CO₂ following door openings, an important consideration in laboratories where cultures must be accessed repeatedly throughout the day.
The chamber is constructed from mirror-finish Type 304 stainless steel for durability, corrosion resistance, and straightforward cleaning. A removable humidity pan provides passive humidification up to approximately 95% RH at 37°C, helping limit evaporation from culture media during extended incubation.
For laboratories that do not need the capacity of a 150- to 250-liter incubator, the Midi 40 offers a particularly efficient use of bench space. Researchers can also use a smaller incubator as a dedicated chamber for a particular cell line, project, investigator, or experimental condition rather than sharing a larger unit across unrelated workflows.
Common Applications
The Thermo Midi 40 is designed primarily for routine CO₂-dependent cell culture and is suitable for research applications requiring stable temperature, humidity, and carbon dioxide concentrations. Typical uses include mammalian cell culture, cancer research, immunology, molecular biology, tissue culture, primary cell research, pharmaceutical development, biotechnology research, and teaching laboratories.
Its relatively small chamber can also be advantageous when experimental segregation is important. A laboratory may dedicate the Midi 40 to a particular project or cell line, use it as supplemental incubation capacity during periods of increased workload, or maintain it as a secondary incubator rather than repeatedly accessing a larger primary chamber.
Cell culture workflows frequently combine a CO₂ incubator with a biosafety cabinet for aseptic handling and a laboratory centrifuge for cell harvesting, washing, and sample preparation. American Instrument Exchange supplies refurbished equipment across these categories for laboratories expanding or replacing existing cell culture instrumentation.
Cell Types & Culture Recommendations
The Midi 40 can support many of the same routine cultures maintained in larger CO₂ incubators, provided the required temperature, CO₂ concentration, humidity, and available chamber space are appropriate for the protocol.
Common Cell Types
Mammalian cell lines
Primary cells
Fibroblasts
Epithelial cells
Immune cells
Hybridoma cultures
Common research cell lines used in pharmaceutical and biotechnology laboratories
Typical Culture Vessels
T-flasks
Multiwell plates
Petri and cell culture dishes
Small media and culture bottles
Other compact vessels compatible with the shelf dimensions
The four-shelf configuration makes the Midi 40 especially useful for small- to moderate-volume culture work. Each perforated stainless steel shelf measures approximately 13.5 × 11.5 inches, allowing researchers to organize cultures across multiple levels without requiring the space or gas consumption associated with a substantially larger chamber.
Environmental Control & Contamination Protection
Consistent environmental conditions are essential for reproducible cell culture. The Thermo Midi 40 combines independent temperature and CO₂ control with passive humidification to maintain the warm, humidified, CO₂-enriched environment required by many mammalian cell culture protocols.
Temperature control accuracy is specified at ±0.1°C, while chamber uniformity is ±0.5°C at 37°C. CO₂ is monitored using a long-life thermal conductivity sensor, with a specified control accuracy of ±0.1%. After the inner door is opened, CO₂ delivery resumes when the chamber is closed and the control system works to return the atmosphere to its programmed setpoint.
The removable humidity pan provides relative humidity levels of up to approximately 95% at 37°C, helping reduce evaporation and associated changes in media concentration during extended culture periods. Incoming CO₂ passes through a 0.3-micron antimicrobial filter, providing an additional measure of protection before gas enters the chamber.
The mirror-finish Type 304 stainless steel interior provides a smooth, non-corrosive surface that can be cleaned as part of routine laboratory contamination-control procedures. For laboratories where frequent high-temperature sterilization cycles are unnecessary, the Midi 40 offers a comparatively straightforward chamber design focused on dependable routine cell culture.
115V, 60 Hz or 208/230V, 50/60 Hz, depending on model
Net Weight
Approximately 60 lb. (27 kg)
Specifications may vary by voltage configuration and production version. Confirm the specifications and included accessories of the individual incubator before purchase.
How much culture capacity does the Thermo Midi 40 provide?
The Midi 40 has a 39.6-liter (1.4-cubic-foot) chamber with four perforated stainless steel shelves. Its compact capacity makes it particularly useful for laboratories running smaller culture volumes or seeking a dedicated incubator for a particular project or cell line.
Is the Thermo Midi 40 suitable for mammalian cell culture?
Yes. The Midi 40 provides the temperature, CO₂, and humidification control required for many routine mammalian cell culture protocols. Researchers should always confirm that the environmental requirements of their specific cell line fall within the incubator's operating ranges.
How does the Midi 40 maintain humidity?
Humidity is generated using a removable water pan inside the chamber. The incubator can maintain relative humidity of up to approximately 95% at 37°C, helping reduce evaporation from culture media.
What type of CO₂ sensor does the Midi 40 use?
The Midi 40 uses a thermal conductivity CO₂ sensor and provides a 0–20% CO₂ control range. This design is well suited for conventional CO₂ cell culture applications.
Why choose a compact CO₂ incubator instead of a full-size model?
A compact incubator can be a better choice when culture volume is limited, laboratory bench space is at a premium, or researchers want to segregate specific cell lines or experiments from cultures maintained in a shared incubator. The Midi 40 provides four shelves of usable culture space while occupying substantially less room than a conventional floor or large benchtop CO₂ incubator.
Is this Thermo Midi 40 refurbished?
Yes. Used Thermo Scientific Midi 40 incubators offered by American Instrument Exchange are inspected and tested prior to shipment and include a 90-day warranty. Available configurations and accessories can vary by individual unit.
Click here to see a video of this incubator on our YouTube channel.
Testing Procedures for Used and Refurbished Laboratory Incubators Ensure Quality and Stability Before Use
Used and refurbished laboratory incubators from American Instrument Exchange are thoroughly tested to ensure optimal performance and temperature stability with laboratory safety standards. Each unit undergoes a detailed inspection and functionality assessment to meet the needs of research, clinical, and industrial labs.
Why Testing Used Laboratory Incubators Is Essential
Before a laboratory incubator is reintroduced into any work environment, it must be tested for:
• Temperature uniformity and accuracy
• Airflow and humidity control (if applicable)
• Door seal integrity and insulation effectiveness
• Electrical and safety system compliance
Comprehensive testing reduces the risk of culture loss, contamination, and equipment failure—especially critical in applications involving cell culture, microbiology, pharmaceutical research, and diagnostics.
Our multi-point testing protocol for used and refurbished incubators ensures reliability, safety, and performance across all models and brands.
Key Testing Procedures for Refurbished and Used Laboratory Incubators
1. Initial Visual Inspection
• Check for cosmetic damage, corrosion, and wear to exterior surfaces, door hinges, and gasket seals
• Inspect power cord, wiring, and display panel for any defects or signs of tampering
• Confirm that shelves, chamber components, and internal fixtures are present and undamaged
2. Functional Testing
• Power on the incubator and verify all display indicators and alarms function correctly
• Test door latch and seal mechanisms for proper closure and insulation
• Run basic temperature cycles to ensure the unit maintains stability over time
3. Temperature Accuracy and Uniformity Tests
• Test internal sensors and controllers using temperature probes
• Measure temperature consistency at multiple chamber locations over several hours
• Confirm that programmable temperature settings respond accurately
4. Airflow and Humidity Control (if applicable)
• Test internal fan operation and airflow distribution
• For humidified incubators, inspect and test humidity reservoirs, sensors, and control systems
• Check for condensation buildup and confirm environmental stability
5. Electrical Safety and Compliance Checks
• Ensure all electrical components are properly grounded
• Perform insulation resistance and leakage current tests
• Verify compliance with current electrical safety standards for laboratory equipment
6. Final Quality Assurance Checklist
• Perform full cycle testing at various temperature setpoints
• Document performance benchmarks and results
All refurbished incubators from American Instrument Exchange are backed by our commitment to quality and precision. With our strict testing procedures, you can rely on your incubator to deliver dependable results from day one.
Repair and Refurbishment Protocol for Used Laboratory Incubators Performance and Quality from American Instrument Exchange
At American Instrument Exchange, every used laboratory incubator we sell goes through a repair and refurbishment protocol. Whether it’s a standard, CO₂, or refrigerated incubator, our goal is to restore each unit to laboratory-level performance—ensuring temperature accuracy, environmental stability, and long-term reliability in your lab.
Why Choose a Refurbished Laboratory Incubator from American Instrument Exchange?
• Fully tested for performance and safety
• Backed by a warranty
• Cost-effective alternative to new equipment
• Environmentally sustainable through reuse and restoration
• Refurbished by expert technicians with decades of lab equipment experience
Step-by-Step Refurbishment Protocol
Every incubator at American Instrument Exchange follows this comprehensive, multi-stage process:
1. Initial Intake & Inspection
• Visual inspection for cosmetic wear, corrosion, dents, or broken components
• Mechanical assessment of door hinges, gaskets, seals, and chamber components
• Document any missing parts or issues requiring repair or replacement
2. Cleaning and Decontamination
• Thorough internal and external cleaning using non-abrasive solutions
• Decontamination/cleaning of surfaces to remove biological, chemical, or particulate residue
• Cleaning of removable parts (e.g., shelves, trays, etc.)
3. Mechanical and Electrical Repair
• Repair or replacement of worn mechanical components such as door latches, fans, hinges, and seals
• Evaluation and repair of control panels, switches, thermostats, and displays
• Inspection and testing of wiring, fuses, relays, and power supplies
4. Environmental Control System Assessment
• For CO₂ incubators: CO₂ sensors, regulators, and gas delivery systems are tested
• For refrigerated incubators: compressors, condensers, and cooling systems are evaluated for performance and leaks
• Fan motors and airflow systems are tested to ensure uniform environmental conditions
5. Temperature and Sensor Testing
• All temperature sensors and controllers are tested using thermometers/probes
• Uniformity and accuracy tested at multiple chamber locations
• For humidified or CO₂ incubators, humidity and CO₂ stability are verified
6. Safety System Testing
• Test of over-temperature protection systems and alarms
• Evaluation of door sensors, safety interlocks, and power failure recovery
7. Final Quality Control and Documentation
• Full performance test run over 24 hours
• Validation of setpoints for temperature, CO₂ (if applicable), and humidity (if applicable)
• Final inspection and cleaning before packaging
• Complete service report
Trust the Experts at American Instrument Exchange
With over 50 years in the lab equipment industry, American Instrument Exchange is a trusted source for high-quality refurbished laboratory incubators. Our proven refurbishment protocol ensures every unit is reliable, accurate, and ready to meet the demands of your lab from day one.
Warranty Information
All used equipment sold by American Instrument Exchange is refurbished/reconditioned, tested to meet specifications, cleaned, and comes with a 90-day warranty from the date of shipment unless otherwise specified. New products include a warranty from the manufacturer. Your warranty is only valid if you have paid your invoice. If your invoice is over 30 days old, warranty work will not be performed until your invoice is paid in full. American Instrument Exchange is not liable for any special or consequential damages that result from the use of, or the inability to use, the materials on this site or the performance of the products,
Exceptions include international sales and items that are agreed to be sold with a lesser warranty or items that are agreed to be sold “as is.”
Should there be visible shipping damage to packaging or concealed shipping damage to item(s) supplied, buyer must communicate such damage to the delivering entity or carrier upon receipt first and to American Instrument the same day item is accepted / signed for. Failure to do so voids warranty. Customer decision to involve / procure third party or OEM service other than American Instrument or AIE assigned vendors to resolve in-warranty instrument failure or defect without first placing a service call to American Instrument voids warranty.
Return & Cancellation Policy
American Instrument Exchange will authorize the return of and issue a full refund for any equipment that is not working as represented and could not be replaced or repaired to the customer’s satisfaction by AIE or a representative of AIE during the warranty period. Returns without prior authorization and an RMA number will not be accepted.
Customers are responsible for proper packaging of the equipment and all included accessories. American Instrument will pay for insurance and shipping costs. Non-inventory items bought specifically to fill customer orders may possibly be returned, but on a case by case basis.
Customers who cancel orders after refurbishing has begun or after delivery where there are no equipment performance issues may be subject to a Restocking/Cancellation Fee of 20% or more and responsible for shipping costs for both the delivery and return.
Ongoing and Extended Support Options
American Instrument Exchange is able to provide additional repair and support services outside the warranty terms for most products that sell.
For biosafety cabinets, clean benches, chemical fume hoods, and other clean air products our team at AIE Laboratory Services can provide certifications, repairs, decontaminations, and other services for customers throughout New England, and guidance and limited technical assistance for any customers in the US and Canada for new or refurbished biosafety cabinets purchased from American Instrument Exchange.
For all other products, the repair service team at American Instrument Exchange can provide both field and depot repair evaluations. We can easily schedule and coordinate the pick-up and transportation of your malfunctioning equipment. By offering hourly rates lower than most OEM service providers and eliminating travel time for technicians, we help reduce repair costs. Furthermore, our lab depot repair service minimizes or eliminates scheduling delays. Our experienced service technicians are qualified to restore your equipment to factory specifications.
Yes, all equipment from American Instrument Exchange comes with a warranty. Used/reconditioned/refurbished equipment is tested to make sure it operates to the manufacturer's specifications and comes with a 90-day warranty (unless otherwise noted). New equipment comes with a warranty from the manufacturer.
How do you test and recondition the equipment?
Testing requirements vary across all the equipment categories we sell. Temperature controlled units are tested with NIST traceable probes and data loggers. Gaskets, external housing, glass, handles, controls and control screens are all thoroughly inspected for integrity and functionality. We test all equipment using the manufacturer's parameters and specifications to confirm that the unit operates properly.
How do products ship from American Instrument Exchange?
We can ship products both nationally and internationally using a well-established network of transporters. Smaller items will ship via UPS. Larger equipment will be palletized and shipped either LTL or air-ride, depending on the specific equipment and/or delivery requirements.
Return and order cancellation policy
American Instrument Exchange will accept the return of any product that is not working as represented and could not be replaced or repaired to the customer's satisfaction during the warranty period. Customers who cancel orders after refurbishing has begun will be subject to a cancellation and restocking fee of between 20% and 40%.
Are discounts available for educational or non-profit institutions, or for bulk purchases?
Yes – call or email us today with a list of equipment you're looking for and we can potentially put together a quote that includes a discount.
How does your price matching policy work?
We strive to keep our pricing competitive and reasonable. If you find comparable items for sale at a lower price from other vendors please send us a link and or quote for the item and we'll do our best to match or beat the price.
Can I see the equipment in person before committing to a purchase?
Customers are welcome to make an appointment to view equipment in our warehouse. Given our workload we may not be able to test or clean the equipment prior to your arrival if you have not committed to an order.
1023 Western Avenue is a working warehouse, not a showroom, and customers should dress appropriately and wear closed toe shoes.
Can I ship products that I purchased elsewhere to American Instrument for repair?
Yes – please see our repair services page for more information.
