Chemical Weighing

Chemical weighing is a term used in pharmaceutical, chemical, biological, and toxicological laboratories to provide maximum containment for weighing operations in weighing scales. In laboratories weighing is generally regarded as a highly hazardous operation because it involves direct handling of pure substances.

Chemical hoods are one of the most important and widely used engineering controls to protect workers in laboratories.

They are also known as fume hoods and were introduced about 100 years ago to safeguard personnel working with hazardous materials.

While many changes and improvements have been made, the basic concept and design of fume hoods remains the same. Air is drawn from the workplace, around the worker and into the front of the hood, and is then exhausted out of the laboratory.

Most laboratory hoods are described as constant air volume (CAV) hoods because they draw a constant amount of air at all times. Rising energy costs have made these hoods exceptionally expensive to operate.

In addition, CAV hoods do not react rapidly to airflow disturbances (turbulence) within the hood or within the laboratory and, hence, their sole purpose of containment and protection can be seriously compromised.

To optimize the effectiveness of properly designed hoods: Maximize capture and containment of hazardous materials Use ergonomic design to enable easy use Conform to high performance standards Minimize energy consumption Insure flexibility to permit quick and easy relocation

The control of hazards is more than simply enclosing the problem. The real questions that should always be asked are how well do the ventilated areas contain the hazards and are the workstations really suitable for the specific tasks being performed.