American Chemical Society (ACS) Laboratory Safety Practice Test

Keeping containers closed except during transfer is crucial for maintaining laboratory safety when working with hazardous materials. Closed containers minimize the risk of exposure to harmful substances, prevent contamination of the materials inside, and reduce the likelihood of accidents, such as spills or releases of toxic vapors. This practice also helps to manage the pressure that can build up due to chemical reactions occurring inside the container.

By only opening the containers when necessary, such as during transfer of the material, you further enhance safety by limiting the amount of time the hazardous material is exposed to the environment and potential hazards, including air contamination and accidental contact. This approach is aligned with good laboratory practices as it protects both laboratory personnel and the integrity of the materials being used.

In contrast, keeping containers open risks increased exposure to chemicals and potential reactions with air or moisture. Leaving containers unattended during experiments poses additional risks, as it can lead to uncontrolled reactions or spills. Closing leaking containers only when they are already a safety concern does not address the critical importance of proactive safety measures.