How can we prevent personnel from inhaling harmful gases during the operation of fume hoods?

Preparations before operation

Check the performance of the fume hood

Test the exhaust function: Before starting the operation, first turn on the exhaust system of the fume hood, place a thin piece of paper or a small strip of paper at the opening of the fume hood, and observe the movement of the paper or strip. Under normal circumstances, paper or strips should be steadily sucked into the fume hood, which indicates that the exhaust function of the fume hood is normal and can effectively discharge harmful gases. If the paper or strips float unstably or cannot be sucked in, it indicates that there may be a problem with the exhaust system. Use should be stopped immediately and professional personnel should be notified for inspection and repair.

Check the sealing performance: Carefully inspect whether the sealing strips of the glass window, cabinet door and other parts of the fume hood are intact, and whether there is any aging, deformation or damage. The function of the sealing strip is to prevent harmful gases from leaking out of the fume hood. If there is a problem with the sealing strip, harmful gases may escape through the gaps and be inhaled by personnel. You can gently press the sealing strip with your hand to check if its elasticity is normal and observe if there are any cracks or notches on the surface of the sealing strip. If any problem is found, the sealing strip should be replaced in time.

Take good personal protection measures

Wear an appropriate mask: Choose a suitable protective mask based on the type and concentration of harmful gases. For instance, for the harmful gases produced by the evaporation of common organic solvents, activated carbon masks can be chosen. Activated carbon can adsorb harmful gas molecules and play a certain protective role. For high-concentration toxic and harmful gases, professional gas masks should be used. Gas masks are equipped with corresponding filter canisters, which can effectively filter and adsorb harmful gases and protect the respiratory system of personnel.

Wearing protective equipment: In addition to masks, other protective equipment such as protective gloves and protective suits should also be worn. Protective gloves can prevent harmful gases from entering the human body through skin contact, while protective clothing can avoid harmful gases adhering to clothes and then coming into contact with the skin or being inhaled. For instance, when conducting experiments involving corrosive and harmful gases such as strong acids and strong alkalis, it is essential to wear acid and alkali resistant protective gloves and chemical protective suits.

Norms in operation

Place the items correctly

Reasonable layout of experimental equipment: When placing experimental equipment and reagents in a fume hood, they should be arranged reasonably to avoid excessive crowding of items, which may affect the flow of air. Equipment or reagents that produce harmful gases should be placed at the rear of the fume hood, away from the operator's position. This way, the harmful gases can be quickly sucked away by the exhaust system after they are produced. For instance, when conducting chemical reaction experiments, place the reaction vessel at the rear of the fume hood and ensure there is sufficient space around it to facilitate air circulation.

Avoid blocking the exhaust vent: Do not place items near the exhaust vent of the fume hood to prevent it from blocking the exhaust vent and affecting the exhaust effect. The exhaust vent is the key part where harmful gases are discharged from the fume hood. If it is blocked, the harmful gases cannot be discharged in time and will accumulate inside the fume hood, increasing the risk of inhalation by personnel.

Standard operation window

Control the height of the viewing window: During the operation, the height of the viewing window of the fume hood should be reasonably controlled according to the needs of the experiment. Generally speaking, the height of the window from the countertop should be 100 to 150mm. This not only ensures ventilation but also protects the upper part of the operator's chest. If the window is too high, harmful gases may escape from above the window. If the window is too low, it will affect the operator's line of sight and operating space.

Avoid frequent opening and closing: Do not frequently open and close the window of the fume hood to prevent affecting the stability of the airflow inside the fume hood. Frequent opening and closing of the window can cause airflow disorder inside the fume hood, preventing harmful gases from being discharged along the predetermined path and increasing the possibility of inhalation by personnel. During the operation process, the window should be kept stably open as much as possible.

Control the operation speed

Add reagents slowly: When adding reagents to the fume hood, do it slowly to avoid excessive evaporation of harmful gases due to rapid operation. For instance, when using a dropper to add liquid reagents to a reaction vessel, the dripping speed should be controlled to ensure that the reagents drip in slowly and reduce the instantaneous release of harmful gases.

Operate the equipment smoothly: When operating the equipment inside the fume hood, do it smoothly to avoid violent vibration or stirring, which may cause the splashing or spread of harmful gases. For instance, when using a stirrer to stir a solution, the stirring speed should be adjusted slowly to prevent the solution from splashing out and generating harmful gases.

Post-operation processing

Continuous exhaust: After the experiment is completed, do not immediately turn off the exhaust system of the fume hood. Let the exhaust system continue to operate for a period of time, usually at least 5 to 10 minutes, to ensure that all harmful gases inside the fume hood are completely discharged. This is because after the experiment, there may still be some harmful gases remaining in the fume hood. If the exhaust system is immediately turned off, these harmful gases will accumulate inside the fume hood and may escape and be inhaled by personnel the next time it is used.

Clean the fume hood: After use, promptly clear the experimental equipment, reagents and waste inside the fume hood, and wipe the interior and exterior of the hood clean. During the cleaning process, it is necessary to pay attention to avoiding the generation of dust or secondary volatilization of harmful gases. For instance, items contaminated with harmful reagents should be placed in designated containers for disposal and must not be discarded randomly in fume hoods. After the cleaning is completed, close the window of the fume hood and the exhaust system.