In recent decades, manufacturers have begun to realize that many processes and
machines operate best at optimum humidity conditions. This thinking is now
being extended to an even more valuable asset...people.
Investigations into Indoor Air Quality (IAQ) show a direct relationship between
the psychological well being of employees and the environment in which they
work. When the indoor relative humidity drops below 40%, the incidence of
absenteeism and respiratory illness increases.
What is Humidity?
Humidity is defined as the amount of water vapor in air. Absolute humidity is a measurement of the actual water vapor in a given volume of air, usually
expressed in grains of water per cubic foot or pound of air. Relative humidity is the amount of water vapor in a given volume of air compared to the amount of water vapor the same volume of air will hold at saturation (100% RH) at a given temperature.
When a volume of air at a known % RH is heated, the % RH decreases as the
volume of air increases. The absolute humidity or total moisture available in the air remains the same. In order to increase the % RH of the air once it has been heated, it will be necessary to add moisture. Example: One cubic foot of air at 0°F holds 0.48 grains of water at saturation. One cubic foot of air at 70°F holds 8.10 grains of water at saturation. When the 0°F air is heated to 70°F, the absolute humidity remains at 0.48 grains per cubic foot. The relative humidity of the 70°F air will be 6% RH, (0.48 grains
divided by 8.10 grains) the amount of water in the 70°F air relative to the amount it can hold at saturation.
Air-conditioning and heating installations are designed for comfort conditions. However, in many cases these systems reduce the humidity below the level recommended for
people to operate at maximum efficiency in a working environment. Only rarely is an HVAC system designed to maintain the controlled relative humidity needed in modern
offices and industry. Therefore, it is strongly recommended to add to the HVAC installation, a carefully designed humidification system to keep the area at the proper RH levels.
Vapor Barriers and Insulation
Water vapor can easily move within a space as well as infiltrate from outdoors or exfiltrate through the building envelope due to vapor pressure differentials caused by different absolute humidity. Under certain temperature and humidity conditions,
condensation problems and possible structural damage can occur. To prevent these problems, Condair recommends that proper design criteria be followed regarding the installation of vapor barriers and insulation in buildings.
Static electricity is a condition caused by stationary charges of electricity and is a major problem in most unhumidified areas. Since static electricity is caused by friction,
particularly when the elements in friction are dry, the problem increases proportionately with the speed of production machinery. Without sufficient humidification, today’s high-speed machinery might well defeat its own purpose. Reduce efficiency is frequently the result of static electricity. For example, when static electricity occurs in fibrous items, the proper operation of production machinery can be disrupted. This applies particularly
to the printing industry where presses must self-feed paper evenly, one sheet at a time at very high speeds. When the static electricity causes sheets of paper to stick together, the paper bunches, the feeding becomes uneven, and eventually the paper jams the presses. The textile industry is another example of a manufacturing process that requires controlled humidity to ensure quality products. For example, if static
electricity causes the yarns to adhere to each other, the shuttles miss threads and
improper weaving patterns result. In the modern business offices, static electricity can disrupt operations and increase operating costs. In many photocopiers, sheets of paper stick together and jam the machine, wasting time and paper. Severely jammed equipment may even require service calls. Static electricity can also be dangerous.
Sparks caused by static are extremely hazardous where volatile fumes are present. Many flash fires - even explosions - are caused by static electricity. Condair humidifiers are designed to eliminate these problems.
Why Relative Humidity Controls Static
Dry air may well be the cause of the static electricity in your plant. If it is, a properly installed Condair humidification system is sure to help solve the problems.
One of the easiest and most common methods of minimizing static electricity
is to increase the relative humidity level. Electrostatic charges do not dissipate through moist air, but through a moisture film that is absorbed on the charged surfaces. This moisture film decreases the surface resistivity and causes static charges to be drained.
This effect is most pronounced at RH above 30-35% and it also corresponds
with a decrease in ozone production (a by-product of electrostatic discharge). In computer rooms and data processing areas, the lack of humidity results in static electricity that causes problems such as circuit board failure, dust buildup on heads, and storage tape breakage. Static electricity is a problem that should be of primary concern to any manufacturing plant interested in running efficiently and accurately.
Moisture stability is the ability of a material to maintain a level of moisture content despite fluctuations the humidity of the environment. Many materials give off, or take on moisture rapidly which can result in serious damage to the material or the process in
which it may be involved. The drying out of a material can result in product deterioration, while conversely, a dry material can also suffer damaging side effects of moisture regain. In many cases, product deterioration is directly related to the lack of moisture stability. Products such as vegetable, cut flowers, fruit and many grocery
items cannot be brought back to original quality once they have lost their moisture.
By installing an efficient humidification system this costly loss of products can be avoided. Today many food processors humidify their plant and storage areas and are able to store fruits and vegetables for months without any loss of product quality or weigh. But deterioration caused by loss of moisture is also a problem for treasures
such as antiques, rare books and the world’s greatest works of art, all of which are susceptible to damage caused by moisture loss. It causes antiques, paintings, paper and bookbindings to crack, warp and deteriorate. Fortunately, most libraries and
museums are well aware of the need for controlled humidity to protect their
priceless treasures. They know that proper humidity control is a very inexpensive, preventive measure that will avoid costly and often impossible restorations.
For any product that requires a certain percentage of moisture to maintain its
quality, loss of that moisture reduces its valve. Some products can be brought
back to their original condition by returning the moisture to them. However, among those that cannot reabsorb moisture to regain their lost quality are fruit and vegetable products, paintings and art objects, what about your product? A specific moisture content in materials is essential to the quality of products produced by a wide range of
manufacturers of hygroscopic or fibrous materials. Wood, paper and textiles are
examples of materials particularly affected by changes in content. If these materials have a correct moisture content when they arrive at a plant, and if they are used immediately, they will respond properly to the manufacturing process. But problems
can be anticipated if the materials are stored in a dry atmosphere. All hygroscopic or fibrous materials either lose of gain moisture in direct relation to the relative humidity of the surrounding air. It is evident that any product that is purchased and sold by weight must have a carefully controlled environment. Paper provides a good example of the
effects of dry air and the lack of moisture stability. When it is stored under dry atmospheric conditions, moisture from the outer layers and edges of the stacks escapes into the air. The moisture loss is obviously much more rapid from the outer edges than from the center of the stacks. The result is not only curled stock, but also uneven moisture content which creates printing and processing problems. If moisture stability in the surrounding atmosphere is the answer to a manufacturing operation, then complete humidification of the plant and storage areas is an absolute necessity.
Humidification is the best and least expensive way of maintaining moisture stability. If the air surrounding the material is maintained at a proper and constant relative humidity level, so that no moisture is emitted or absorbed by the materials, then the products will remain stable in both moisture content and dimension. Ideally, humidification equipment should be installed in raw material storage areas, manufacturing facilities, and finished goods’ storage rooms, for full control of the product moisture content.