Heat Sources in a Biosafety Cabinet Compromise Experimental and User Protection.

Introduction: Keeping a contamination free environment in the laboratory has commonly been achieved by one of two ways: a flame or a biosafety cabinet (BSC). However, it has been frequently observed that these two practices have been combined, where a heat source has been used within the BSC. As flames require flammable gasses and cause hot air to rise, it was hypothesized that these could lead to a loss of BSC containment, as BSCs rely on unidirectional downflow air. Objectives: The objective of this study was to determine whether BSCs can maintain containment when a heat source is operated within the work area. Methods: Several heat sources (Bunsen burner, High Heat Bunsen Burner, Spirit Lamp and Bacti-cinerator) were placed within two sizes of BSCs (4-foot and 6-foot), and smoke was used to visualize airflow disturbances, air cleanliness was measured by particle counting , and aerosol microbiological testing was conducted to ascertain containment. The risk of introducing a flammable gas into a BSC was also calculated. Results: Large flamed Bunsen burners were found to have the most detrimental effects on the ability of the BSC to maintain containment, especially in the center of the work area, while the smaller heat sources were more variable. Containment was completely lost in the 4-foot BSC, whereas the 6-foot BSC was capable of maintaining containment in only a few conditions. The BSC was also calculated to be able to maintain the required volume of flammable gas needed to operate the burners, not taking into consideration unintended leaks. Conclusions: Overall, it was determined that BSCs cannot operate safely and reliably while housing a heat source, as it could cause unexpected contamination of the work or the worker, or BSC ignition or explosion.