Environmental Test Chambers

Chapter One – What is a Test Chamber?

A test chamber is a managed and controlled environment used to test the endurance, stability, and practicality of equipment, products, and chemicals. They are a controlled enclosure that mimics the effects of environmental conditions that a product may encounter during its usage. Programmed test chambers create extreme temperature variations, moist or humid conditions, and radical altitude variances.

Aside from environmental conditions, test chambers can be designed and set to push the limits of a product through the use of physical forces such as inertia, vibration, and destructive impact.

The burst test, seen in this image, determines the amount of resistant pressure this sample of cardboard can endure before it fails, an example of the types of endurance testing performed in test chambers.

Some of the other purposes for test chambers are:

• Prepping a product for additional testing
• Stand alone testing for combinations of different materials
• Stress screening to help identify product issues while still at the prototype stage

Chapter Two – What are the Designs of Test Chambers?

Test chamber designs vary depending on the types of test they perform, which can be very complex and complicated or extremely simple. They come in various sizes to fit the manufacturer and the desired conditions to be tested such as a bench top for testing small items and room size to fit a car.

Though size and types of environments are a factor, modern test chambers have technological controls that can provide instantaneous data and read outs that give technicians the opportunity to adjust and change conditions in the middle of a process. In a steady test chamber, pictured below, a specific set of variables are programmed into the chamber and remain unchanged for extended periods.

Steady test chamber are specially designed to maintain a constant and accurate temperature as a part of the age testing. They have duct and electrical control systems that are able to sustain an environment for long intervals.

Factors in the Design of a Test Chamber:

Size

The size of a test chamber depends on the type of product to be tested. Sizes vary from one cubic foot to 12,000 cubic feet, large enough to fit an airplane. Below are images of two types of test chambers. The first is an ISO small environmental test chamber for industrial hot air dryer testing. The second is a walk in that creates various temperature levels and humid conditions. It is 8’x4’x4’ and has a wind driven rain machine with a wind turbine that can produce winds up to 160 mph.

Controllers

Test chamber controls allow technicians to monitor testing from their desk top computer or laptop. A view of set points, temperatures, and humidity are readily available with preset graphics or ones that can be customized to a customers special conditions. Unlike older model test chambers that provided data at the end of a test, new technology allows users to monitor and adjust test conditions as the test is in progress. As can be seen on the controller display below, it is possible to monitor air temp, product temp, and humidity digitally and graphically with data being sent every second.

Automated

Automated test chambers can be programmed in a variety of ways to produce multiple environmental conditions in succession. A series of steps can be programmed into the chamber that can include ramp, soak, jump, and auto stop and start. The purpose of an automated chamber is test the endurance and durability of a product. Its system depends on a ruggedly built Programmable Logic Controller (PLC) that is designed to perform in industrial settings. Pictured below is a laptop that is being tested in an automated test chamber.

Photostability

Photostability testing creates exposure levels to the full spectra of light a product can experience during its use. The testing chamber provides a precise analysis of the effects of sunlight, UV rays, and various colored lights, which can cause color fading or product deterioration. Data is provided regarding visual color assessment, comparison of color variations, and detection of metamerism, in colorimetry, the matching of colors with different spectral power distributions.

For critical health products, such as medications and drugs, photostability chambers create forced degradation, extreme conditions beyond the normal environment. Photostability testing has become common since 1990 for pharmaceutical, paint, ink, and dye manufacturing industries.

The International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) has specific standards for photostability testing under provision Q1B, which allows for two light source options for pharmaceutical testing. The Q1B test indicates that there are no unacceptable changes from a light source.

Pictured below is a photostability test of golf ball sized spherical sensors to measure the effects of UVA and visible light (VIS).

Chapter Three – Types of Test Chamber Tests

In the R and D (research and development) stage of product development, prototypes of a product are subjected to tests to determine its reliability, durability, resistance to a variety of climactic and environmental conditions, and its behavior during normal use. Any failure at this stage causes engineers to examine the products defects and work on correcting the problem.

The types and number of tests vary depending on the industry, such as segments of the auto industry may emphasize the durability of paint, while other departments test stress and perform structural analysis. Testing has become essential in modern industry. Below is a list of common forms of testing.

Types of Tests:

Temperature Test

Temperature test is the most common product stress test since fluctuations in temperature cause a product to expand or contract. Rates of temperature changes are determined by the type of product being tested. Temperatures can range from a -80o C to a +250o C (-112o F to 482o F).

Humidity Test

Humidity test is the second most common form of environmental stressor that can affect the internal workings of a product. Moisture or leakage lead to oxidation and corrosion.

Accelerated aging Test

uses a set of atmospheric conditions to speed up the aging process to determine how long the product will last. It is mainly used with new products that have not been through the normal aging process. A full spectrum tests are used from temperature and humidity to shake and vibration. The chart below is a graph of the aging process of the degradation of the luminous flux of a LED light.

Agree Test

Agree test combine temperature and humidity testing with vibration testing. They create rapid temperature changes with varying humidity. The vibration test measures a products reaction when being shipped or moved.

Thermal shock Test

is testing that verifies the reliability of a product during rapid changes in temperature, which are more severe than the expected range a product may experience. It is used to determine cracking and strength of bonding materials.

Altitude Test

Altitude tests the adaptability and reliability of a sample under low pressure, high temperature, and altitude, while measuring electrical performance parameters. Temperature altitude test chambers test vehicles, computers, and electronic components for high mountain conditions as well as packaging for air transport.

Moisture Test

Moisture test simulate soaking and rainy conditions. They use water tight chambers for water spray testing and have a self-contained recirculation systems. Water is injected by nozzles with flow meters to adjust the water supply.

Electrodynamic vibrations Test

Electrodynamic vibrations test or shaker systems conduct shock, vibration, and stress screening for failure analysis of pcb electric boards, mobile phone chips, aerospace equipment, military aircraft, automotive parts, tanks, and heavy weapons and equipment.

Electromagnetic radiation Test

Electromagnetic radiation test is a test for the flow of electromagnetic waves from a product, is a required test by several nations, and must be repeatedly performed on production models.

Cyclic corrosion Test

Cyclic corrosion test accelerates the corrosion process in laboratory conditions and is widely used in the auto industry. Materials may be submerged, dried off, or sprayed. The test is complicated and involves multiple exposure processes.

Salt spray Test

Salt spray test is another accelerated corrosion test that exposes a sample to a salt spray or salt fog. The test chamber subjects the sample to a constant and continuous indirect application of fog or spray.

Climactic Test

Climactic test is testing that creates a controlled setting for all types of weather conditions to determine the reliability and longevity of a product. Climactic testing includes many of the other forms of testing, such as temperature, humidity, corrosion, and sand and dust.

Sand and dust Test

Sand and dust test is a form of testing that circulates sand, dust, and other possible contaminants at high speeds in the testing chamber. Particulate count and speeds are adjusted in accordance with preset specifications for the material to be tested.

Vacuum Test

Vacuum test are tests that are mainly performed on equipment that will be used in outer space or processes that include vacuum drying or coating.

Cytogenetic Test

A cytogenetic test is designed for slide drying tests for the creation of situ and non-in situ cell samples. For the best results, control of the temperature and humidity must duplicate the environment conditions for chromosome spreading. The results of a chromosome analysis depends a great deal on the conditions where the evaporation of the methyl acetate or ethyl acetate fixatives happens.

Stability Test

Stability test is a type of test designed to present evidence on how the quality of a drug will change over time under the influence of a variety of environmental and atmospheric factors. The most common factors are temperature, humidity, and light. The results of the test outline recommendations for storage conditions, when to retest, and shelf life. The guidelines for testing are outlined in Federal Drug Administration (FDA) Q1A(R2) titled ““Stability Testing of New Drug Substances and Products”.

Aside from photostability testing, other drug stability tests include accelerated, intermediate, freeze and thaw, bulk holding, and period after opening (PAO). A further requirement of the FDA is expiration dating, which has to be supported by real time (RT) stability testing.

Excursion

Excursion is a time temperature sensitive pharmaceutical product test where the product is exposed to temperatures that are outside the normal range provided for transport and storage. The difficulty of excursions is that they can happen at any time, which means that transport is the most vulnerable time for pharmaceutical distribution.

The difficulty of excursion testing is that there isn’t any possible means for predicting what conditions will create an excursion. Disasters, weather changes, and improper handling can all lead to excursions. The best tests increase the rate of chemical degradation or other possible change radically adjusting and modifying possible storage conditions as part of a stability test.

Chapter Four – Types of Test Chambers

Most test chambers are designed to perform more than one type of test to save money and time. Specially designed chambers test the viability of a new product that is about to be introduced. The majority of chambers do temperature and humidity testing or stress and vibration endurance testing. A select few perform highly accelerated stress screening (HASS) or Highly Accelerated Life Testing (HALT).

The use of test chambers has become a critical part of modern product development, testing, and marketing. Listed below are a few of the different types.

Types of Test Chambers

Mechanical Test Chambers

Mechanical Test Chambers perform mechanical tests, such as hardness, shock, vibration, impact, fracture, and fatigue. In some industries, they are known as shakers. The image below is of a tensile testing machine.

Walk in Test Chambers

Walk in Test Chambers are large enough for a person to walk in. They vary in size from a small closet to ones that can fit a car or truck, as seen below, capable of completing the full range of tests from thermal shock and salt spray to humidity and temperature variances. The YouTube video below is from a Ford testing center performing a cold weather test on trucks and cars.

Modular Test Chambers

Modular Test Chambers are pre-engineered and prefabricated to be assembled to meet any type of testing need. They include modular electrical temperature control systems that can be adapted to meet any set of desired conditions.

Table top Test Chambers

Table top Test Chambers are designed to test small items but have the same functionality of larger chambers with variations in temperature and levels of humidity. They come in a variety of sizes from one to four cubic feet.

Steady Test Chambers

Steady Test Chambers perform long term shelf life material testing and are capable of simulating a wide range of humid environments and temperatures. Types of tests include accelerated aging, packaging, life science, storage, and research.

Anechoic or EMC Test Chambers

Anechoic or EMC Test Chambers are lined with sound and electromagnetic absorbing material to shield against attenuated electromagnetic interference. They test the radiated emissions of a product or its immunity to radiation emissions. Since the chambers are shielded against outside interference, an operator gets an accurate measure of the EMC field generated by a device and can determine if a piece of equipment complies with emission standards. The image below is of the interior of an anechoic chamber.

Cryogenic Test Chambers

Cryogenic Test Chambers create extremely low temperatures. Using liquid nitrogen or helium, a cryogenic chamber can reach temperatures as low as -238° F or -150° C. They are time consuming and costly since the temperature has to be lowered very slowly. The picture below is of a large walk in chamber testing an airplane at extremely low temperatures.

Pressure Test Chambers

Pressure Test Chambers place products under extreme pressure. They simulate static and changing pressures at high altitudes and ocean depths. Pressures can reach as high as 60,000 psi or be reduced to create a vacuum.

Remote conditioners Test Chambers

Remote conditioners Test Chambers can go to large products or ones that are hard to reach. They have flexible temperature settings for secluded locations and can create temperature variations, humid conditions, and are cost effective.

Stability Test Chambers

Stability Test Chambers have a controlled environment where all variables are held constant, while others are being modified for testing. They are primarily used to test temperature and humidity ranges but can do shelf life testing.

Vacuum Test Chambers

Vacuum Test Chambers remove air and pressure from a sealed compartment to evaluate the effects of a vacuum. Testing by a vacuum test chamber is a requirement of the aerospace and defense industries. Spacecraft engineers use it for testing electronics, circuits, lenses, filters, and structural materials.

Welded Test Chambers

Welded Test Chambers are ideal for applications that require high temperatures over 93o C, high humidity, rapid temperature changes, and altitude simulations. They have one piece construction and a hermetically sealed steel frame.

Reach in Test Chambers

Reach in Test Chambers are a form of remote conditioner that is portable and can simulate any form of environmental conditions. They are a very convenient method for botanical and biological research.

Chapter Five – Test Chamber Industry Applications

For several decades, test chambers have been used to study products for aerospace, artificial intelligence, automotive, electronics, solar cell, medicine, and industrial research. They offer a convenient, economical, and efficient method for studying products during development, production, and distribution.

Since their development, test chambers have found use in almost every aspect of manufacturing. Below is a brief sampling of industries that use testing chambers.

Industrial Applications

Auto industry

In the auto industry, test chambers provide artificial space to recreate possible conditions vehicles and their parts may confront during their lifetime. Test chambers allow engineers to accelerate conditions to determine the resilience of materials.

Aerospace industry

The aerospace and aviation industries use test chambers for testing of atmospheric conditions for adherence to stringent SAE standards. The three critical factors for testing aerospace equipment are quality, reliability, and safety. The nature of aerospace manufacturing requires producers to follow a variety of regulations and requirements. The YouTube video below explains about anechoic testing of electronic equipment for antennas and satellites.

Pharmaceutical industry

The main forms of pharmaceutical testing are steady, accelerated aging, shelf life, and expiration date. As with the aerospace industry, pharmaceutical companies have very strict and stringent regulations that determine their production methods. Testing of medicines is one of the most crucial factors.

Battery industry

The battery industry uses testing chambers to test their products for vulnerability to humidity, heat, and vibration. HASS and HALT testing is used to simulate types of failure conditions. The fragile nature of batteries requires highly precision testing and assessment. To ensure quality, batteries are put through every possible test from altitude simulation to thermal shock. The image below is of a set of batteries that are beginning the testing process.

Chapter Six – Test Chamber Standards

Standards and regulations regarding the production of industrial equipment are used to determine the quality of the data and the safety of users. Unlike other products, test chambers have a very long list of certifying organizations that specify the requirements and specifications for test chamber classifications. The best known and most commonly used designations have been developed by the International Organization of Standardization (ISO).

Companies can choose the set of standards they will follow. Critical industries, involved with public safety, are required to meet specific regulations. Most manufacturers work to get approval of as many certifying organizations as possible.

Below is a list of a few of the certifying organizations.

ISO

The International Organization of Standardization is an independent, non-governmental membership organization and the world's largest developer of voluntary international standards. The ISO specifications for test chambers are 10605 for electrostatic discharge, 16428:2005 for surgery implants, 16525-7:2014 for adhesives, 7137:1995 for airborne procedures, and 9022-20:2015 for optics and photonics.

AECTP 100

The North Atlantic Treaty Organization (NATO) provides guidance for the handling of military equipment in the Allied Environmental Conditions and Test Publication (AECTP) 100, Environmental Guidelines for Defense Material. AECTP 100 includes a list of requirements regarding the handling of various types of ordinance.

ASTM

The American Society for Testing and Materials standards for aerospace, automotive, building and construction, chemicals, consumer products, food processing, medical devices, IT, telecommunication, manufacturing, pulp & paper, safety and security.

ASTM was developed in the United States to address manufacturing quality issues. It has expanded to 140 countries and has 1,150 participating organizations.

FDA

The United States Food and Drug Administration was legislated for the protection of the public. It specifies requirements regarding the quality and purity of products.

IEC

The International Electrotechnical Commission publishes standards for electrical, electronic and related technologies.

JEDEC No. 22-A104D

Joint Electron Device Engineering Committee develops standards for microelectronics. Its goal is to serve as an oversight for microelectronics technology. In its sixty years of existence, it has developed testing methods and product standards for the semiconductor industry.

MIL-STD

MIL-STD was developed by the United States Department of Defense. The purpose of MIL-STD is to provide suppliers with a set of standardized directions for the production of military weapons and equipment.

RTCA

Radio Technical Commission for Aeronautics is dedicated to bringing organization to the complex issues regarding the aviation industry. It has published standards regarding every advancement in aviation and methods for testing aerospace instruments and equipment.

SAE

The Society of Automotive Engineers International focuses on the development of standards for the transportation industries. Most testing organizations that supply the automotive, truck, and aircraft industries strive to get SAE certification.

SR-332 (Telcordia)

Issue 4 of SR-332 provides methods for predicting the reliability of hardware. Known as the Telcordia Reliability Prediction Procedure, it uses data collected from major companies to develop ways to predict the success of equipment.

UL

Underwriters Laboratories conducts research and analysis regarding safety to develop standards to guide commercialization of technology. It provides safety certifications, validations, testing, inspection, auditing, advising, and training.

UN/DOT 38.3

UN/DOT 38.3 is a set of regulations regarding the transportation of lithium batteries. It has been adopted as a global standard.

Conclusion

• Test chambers are a managed environment designed to test products in a controlled environment.
• There is a wide spectrum of tests that can be performed in a test chamber with temperature and humidity being the most common.
• Test chambers come in a variety of sizes from one cubic foot to several thousand and can fit on a counter top or an airplane hanger.
• Testing of products has become more essential as the demands of customers have risen and products have become more technical.
• There is a wide array of organizations that have developed standards for test chambers.
• Every industry has invested in test chambers for the testing of products from development through production.