Companies across nearly every commercial industry utilize environmental testing to confirm that their products or components work as intended and to understand when they fail.
Often in the real world, heat and humidity lead to failures.
That’s why it’s important for manufacturers to create these conditions in a controlled working environment, a method known as humidity testing. Top-of-the-line temperature and humidity chambers enable users to precisely manipulate settings to meet testing standards.
This enables you to evaluate the performance of your products and set expectations for consumers.
What Is Humidity Testing?
Humidity testing is the process of determining how products or devices under test (DUT) withstand real world conditions by subjecting them to controlled humidity environments. This type of testing is completed using humidity chambers. Humidity chambers are environmental test chambers that use vapor generator systems to create specific levels of moisture and heat within the chambers’ workspace. Humidity testing is commonly used in industries ranging from packaging to electronics, pharma, communications, and military defense.
So how does a humidity chamber create these conditions?
As temperature increases, the air’s capacity to hold moisture increases, as well. That’s what relative humidity (RH) refers to—the level of humidity attainable at a given temperature. Since warmer air holds higher amounts of water, RH at 5 degrees Celsius, for example, will be lower than RH at 20 degrees. This is not to be confused with dew point, which is the temperature at which air must be cooled for it to condense or form water droplets.
The temperature changes and humidity source must work together to reach the desired setting, informed by industry testing standards.
To do this, you need precise control, which test chamber manufacturers can accommodate with an advanced vapor generator system. Vapor generators (closed stainless steel or copper tubes) can be customized to fit any chamber. Multiple generators can be used for larger workspaces to increase accuracy, as well. Using properly conditioned water, a heating element produces vapor or steam that mixes with conditioned air in a plenum before entering the workspace. You’ll often see manufacturers add demineralizing cartridges to humidity chambers for this purpose
Electric sensors provide highly accurate readings to ensure the condition of the workspace meets your requirements.
This modern system has replaced older methods of creating humidity, such as immersing heaters in water pans or relying on atomizing nozzles (today, you’ll find atomizers on salt spray chambers). Standard humidity chambers feature an RH range of 10% to 95%, with dehumidification coils helping the workspace reach lower humidity levels: The coil attracts moisture, which condenses and drains out of the chamber.
High humidity sensors can be added to reach RH as high as 98%. If you need to create conditions less than 10% RH, you can typically do so in three ways:
Nitrogen Purge
Because nitrogen gas is naturally dry, it’s slowly added to the workspace to push out the moisture-laden air. Nitrogen also prevents the oxidation of metals and frost from accumulating on the surface of DUTs.
Dry-Air Purge Through Desiccant Air Dryer
In a dry-air purge, external compressed air goes through a desiccant system, which absorbs the moisture, before entering the workspace.
Recirculating Desiccant Air Dryer
For larger chambers, nitrogen or a standard dry-air purge might prove impractical. As an alternative, the chamber air is circulated through a desiccant then returned to the chamber. Part of the desiccant system, often in the form of a honeycomb wheel, releases captured moisture to the external workspace.
The relative humidity you need to reach should be a main point of discussion when purchasing a test chamber.
You can even use a manufacturer-developed dew point calculator to determine if you'll require optional boosts.
Use Cases for Temperature and Humidity Chambers
Humidity is often a key component of highly accelerated life testing (HALT) or highly accelerated stress screening (HASS). The set conditions, determined by the standards you’re testing to, simulate the lifespan of products. In HALT testing, the goal is to find out when products fail over time. A change in conditions corresponds to a specified number of years in a real-world environment. HASS testing, on the other hand, exposes products to extreme conditions to prove their quality before going to market.
The results are crucial to setting expectations for customers (in the form of warranties and expiration dates) and ideal conditions: how to ship, store, and operate the product without failure.
That applies to a number of industries.
Electronics companies need to ensure their phones, tablets, and laptops work in a variety of climates (the high humidity of the coasts and the dry, extreme heat of the deserts). The same is true of manufacturers of electric vehicles and airplanes, which, if they malfunction, pose a safety threat.
Even packaging plays a crucial role, from choosing the appropriate materials for pharmaceuticals to creating shipping and storage boxes that will protect the contents over time.
Each industry features its own standards (and companies themselves establish internal criteria as well). Here are some common standards that require a humidity component:
- The U.S. Department of Defense developed the MIL-STD-810 to evaluate equipment’s performance when exposed to different environmental conditions and identify any weaknesses in the equipment.
- RTCA DO-160 uses humidity to determine thermal expansion in the aviation industry and requires extreme temperature changes.
- In the telecommunications industry, GR-1081 specifies test procedures for fiber optics.
- The International Standardization Organization (ISO) has published thousands of standards that run the gamut from imaging materials to combustion engines and medical devices.
- The International Electrotechnical Commission (IEC) sets testing requirements for electrical, electronic, and related technologies such as power generation, semiconductors, and fiber optics in these industries: batteries, solar energy, nanotechnology, marine energy, and more.
- The International Safe Transit Association (ISTA) has developed standards for the packaging industry to minimize product damage throughout distribution.
- SAE International develops and advances standards for companies in aerospace, commercial vehicles, and automotive engineering.
These are only a handful of the many standards that include humidity components. Some are specific to industry and country, while others are international. That’s why it’s so important to understand your testing requirements before purchasing a test chamber. Working with an experienced manufacturer can help you determine whether you should outsource testing or better off buying a humidity test chamber.
Associated Environmental Systems builds custom test chambers to fit your specifications—with optional features such as high humidity sensors and desiccant air dryers, not to mention AESONE CONNECT, a combination of software and hardware that enables remote monitoring—and carries standard temperature and humidity chambers in stock.
AES also offers support and service plans throughout the life of its chambers. You’ll test as often as you want, with a leading test chamber manufacturer on your team. Contact us to learn more today.
