The procurement specification said "climatic test chamber." The laboratory had a thermal chamber. The engineer who wrote the specification and the engineer who reviewed the purchase had both assumed they were the same thing. They are not.
A thermal chamber controls temperature. A climatic test chamber controls temperature and humidity simultaneously. The distinction seems minor until the test programme requires 85°C / 85% RH — a condition that a thermal chamber, with no humidity generation or control system, cannot produce. By the time the error was discovered, the purchase order had been placed and the lead time had started.
The terminology around environmental test chambers is inconsistent across manufacturers, standards bodies, and engineering disciplines. "Climatic chamber," "climate chamber," "climatic test chamber," "temperature humidity chamber," and "environmental test chamber" are used interchangeably in common usage — and refer to different things in technical usage. This guide maps the distinctions.
What a climatic test chamber is
A climatic test chamber is an enclosure that controls both temperature and humidity simultaneously to defined setpoints. An environmental chamber — also called a climatic chamber or climate chamber — is an enclosure used to test the effects of specified environmental conditions on biological items, industrial products, materials, and electronic devices and components.
The defining characteristic of a climatic chamber is the humidity control system — a steam generator, ultrasonic humidifier, or water injection system that introduces controlled moisture into the test volume, combined with dehumidification capability (typically through cooling below the dew point and reheating) to reduce humidity when required. Without this system, a chamber can control temperature but cannot control humidity. That chamber is a thermal chamber — useful, but a different instrument.
Climatic vs thermal — the key distinction
A thermal chamber controls temperature only. It has a refrigeration system and heating elements, and can ramp and hold temperature across a defined range. It does not have a humidity generation system. It cannot control relative humidity. In a thermal chamber, the humidity in the test volume is whatever the ambient humidity of the air happens to be at the operating temperature — which, particularly at elevated temperatures, will be far below any meaningful humidity setpoint.
A climatic chamber adds humidity control to the thermal chamber capability. It includes everything a thermal chamber has — refrigeration, heating, air circulation, and temperature control — plus a humidity generation system, a humidity sensor, and a control loop for relative humidity.
The cost premium for humidity control is real and significant. If the test programme does not require humidity control, specifying a climatic chamber adds cost without adding value. If the programme does require humidity control — now or in the foreseeable future — specifying a thermal chamber creates a capability gap that cannot be retrofitted.
What climatic chambers test — the IEC 60068 framework
The IEC 60068-2 series defines the test methods for environmental testing. Climatic chambers are the primary equipment for the following IEC 60068-2 tests:
Exposure to specified low temperatures. Climatic chamber required; humidity control not mandatory for this test but typically available.
Exposure to specified high temperatures at low relative humidity. Thermal or climatic chamber.
Method Nb — temperature cycling with controlled ramp rate. Climatic or thermal chamber. Method Na — thermal shock — requires a two-zone thermal shock chamber.
Requires humidity control. Climatic chamber mandatory. Typical conditions: 40°C or 55°C at 93% RH.
Requires cyclic humidity control — the chamber must ramp both temperature and humidity through a defined cycle. Climatic chamber mandatory.
IEC 60068-3-11:2007 uses "climatic test chambers" as the standard term for temperature and humidity chambers — demonstrating how the IEC itself uses "climatic" to mean T/H capability, not temperature alone. When a test standard references a "climatic test chamber," it means a chamber with humidity control.
Climatic vs altitude chamber
An altitude chamber — also called a low-pressure chamber — reduces atmospheric pressure inside the test volume to simulate the reduced air pressure at altitude. A standard climatic chamber operates at sea-level atmospheric pressure and cannot simulate altitude regardless of its temperature range.
Some combined chambers control temperature and pressure simultaneously — essential for tests such as DO-160G Section 4 (altitude and temperature combined) and MIL-STD-810H Method 520 (combined environments). These are distinct from standard climatic chambers and significantly more expensive and specialised.
A climatic chamber cited for an altitude test is a non-conformance. The standard that requires altitude testing — MIL-STD-810H Method 500, DO-160G Section 4 — requires reduced pressure. A climatic chamber cannot provide this.
Climatic vs combined environment chamber
A combined environment chamber applies multiple stressors simultaneously — most commonly temperature, humidity, and mechanical vibration in a single test sequence. This requires a climatic chamber with an integrated vibration table or a vibration table installed inside the climatic chamber volume.
A standard climatic chamber without vibration capability cannot conduct combined environment testing. Running temperature cycling on a climatic chamber and vibration testing on a separate shaker — sequentially, not simultaneously — is not the same as combined environment testing. MIL-STD-810H Method 520 requires simultaneous application. Sequential tests do not replicate the combined stress environment.
Walk-in vs reach-in climatic chambers
Climatic chambers are available in two physical configurations that are relevant to most procurement decisions:
Reach-in chambers — free-standing cabinets with front-access doors, internal volumes typically from 20 litres to 2,000 litres. The DUT is placed inside through the door. Access during the test is possible through glove ports, cable feed-throughs, or door openings. Most standard component and product-level testing uses reach-in chambers.
Walk-in chambers — room-sized enclosures where personnel can enter the test volume while the chamber is operating (within safety limits). Internal volumes from approximately 4 m³ to 50 m³ or larger. Required when the DUT is too large for a reach-in configuration — vehicle components, large assemblies, battery packs, aircraft sections.
The key specification error in walk-in chamber procurement is using nominal volume instead of usable workspace volume. A chamber with a nominal volume of 20 m³ may have a usable workspace of 12–14 m³ after accounting for refrigeration equipment projections, structural elements, minimum clearance requirements, and door swing. This is the failure documented in Case #006.
How to specify one
A climatic chamber specification must include performance requirements — not just equipment ranges. The parameters that determine whether the chamber is suitable for the test programme:
Temperature range. Minimum and maximum setpoint at full load. Not the empty-chamber rated range — the achievable range with the DUT configuration installed.
Temperature stability. ±°C deviation from setpoint at the DUT sensor during steady-state operation. Typically ±0.5°C to ±2°C depending on application. ICH Q1A requires ±2°C.
Humidity range and stability. The RH range and the ±% RH stability tolerance during steady state. State the temperature range over which humidity control is required — not all chambers maintain humidity control at the extremes of their temperature range.
Ramp rate. At the DUT surface under load — not the chamber air sensor rated value.
Usable workspace volume. Explicitly specified as usable volume after shelving and clearance, not nominal internal volume.
Refrigerant compliance. Under Regulation (EU) 2024/573, any chamber supplied to the EU market from 2025 must use a compliant refrigerant. Specify R-449A or CO₂ (R-744) as the requirement. Exclude R-404A.
What IEC 60068-3 requires for performance verification
After delivery and installation, a climatic chamber must be verified to confirm it performs to specification in its installation environment. IEC 60068-3-6:2018 provides a uniform and reproducible method of confirming that temperature and humidity test chambers, without specimens, conform to the requirements specified in climatic test procedures of IEC 60068-2.
The verification process requires temperature and humidity sensors distributed across the workspace volume at defined positions, held at each specified setpoint for a minimum stabilisation and measurement period, with the data demonstrating that stability and uniformity meet the specification. A signed verification report before the chamber is placed into service is the minimum documentation standard.
IEC 60068-3-6:2018 — Confirmation of the Performance of Temperature/Humidity Chambers. IEC.
IEC 60068-3-11:2007 — Calculation of Uncertainty of Conditions in Climatic Test Chambers. IEC.
Regulation (EU) 2024/573 of the European Parliament and of the Council on fluorinated greenhouse gases. Official Journal of the European Union, 2024.
The terminology distinction between climatic, thermal, altitude, and combined environment chambers is not academic. Specifying the wrong one closes a capability gap that cannot be retrofitted.
Read the buyers guide before specifying →Frequently asked questions
What's the actual cost difference between a lab-caught failure and a field failure?
Industry rule-of-thumb places field failures at 10 to 100 times the cost of catching the same defect in a test chamber, once warranty claims, recalls, and reputational damage are included — though the exact multiplier varies heavily by industry and failure severity.
Can a single chamber test both temperature and humidity, or do I need two separate machines?
A climatic chamber tests both in one unit, using a humidity generator alongside the refrigeration system. A pure temperature chamber has no humidity control at all — the distinction matters because climatic chambers cost more and have a narrower usable temperature-humidity combination range.
Does an environmental test chamber actually predict field reliability, or just compliance?
Neither automatically. A chamber only predicts field reliability if the test conditions were derived from measured field data — not from a standard's default values. Compliance with a standard's default conditions tells you the box was checked, not that the product will survive deployment.
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