Wood as we all know is extensively used and a great building material. Wood is considered as strong, lightweight, relatively inexpensive and can easily be worked with different kind of tools. One of the biggest problems with wood is that it is easily flammable and also can attract various kinds of bacteria, insects, fungi easily and therefore may not suit under number of conditions. In case wood remains in contact with any moisture or ground for longer period of time, then any of these organisms can attack wood. Any untreated wood for example, pine can only last for one to two years, if it remains in touch with moist ground.
Any pressure treated lumber may also be a wood but it has been treated by immersing in certain liquid preservative and also placed in pressure chamber. The chamber will force the chemical which will enter into the fiber of wood. By using pressurized approach, it will ensure that all the chemicals become core of every piece of wood. This will be much more effective as compared to simply soaking them in the chemical.
Among the chemicals used for the treatment of lumbers are Chromated Copper Arsenate (CCA). In the year 2003, Environmental Protection Agency had restricted the use of CCA for residential uses due to various health and environmental reasons and presence of arsenic compound that is leaching out of wood. Other most widely used chemical as an alternative to CCA can be Alkaline Copper Quat (ACQ). Copper can be toxic to number of fungi and insects that can cause decay. ACQ can bind wood fibers quite well and can allow wood to last for decades despite remaining in contact with water or ground.
The amount of protection offered by the chemical will depend upon amount of chemical the wood can absorb. In the USA, the chemical amount is generally measured in pounds/cubic foot of wood. For any ground contact, 0.40 pounds/cubic foot will be needed and for foundations it will be 0.60 pounds/cubic foot which is the standard.
Any chemically treated woods are not generally considered good for humans. Therefore, you may find warnings advising you about wearing gloves, avoid burning treated wood or breathing the sawdust. It is also important to keep small children out of reach from such treated woods.
Though this pressure treated lumbers do not need any extensive maintenance however periodic coating of water repellent can help to maintain their appearance of the project.