David Phillips, Technical Applications Specialist - Laminar Flow, Thermo Fisher Scientific
Managing groups of biological safety cabinets (BSCs) in a biomedical research, healthcare or academic facility requires three strategies to optimize the total cost of ownership. These strategies address both performance and cost. An inexpensive BSC that does not provide the needed cleanliness and containment has no value to an institution; conversely, a BSC device that provides unneeded or unused protection is a waste of important resources that could be better utilized elsewhere.
Strategy One: The Right Tool For The Job
BSCs, clean benches, chemical fume hoods and all other airflow cabinetry are all commonly called “hoods”. Although the laboratory hoods are often lumped together, they provide very different types of protection with different TCO structures.
BSCs, laminar flow clean benches and cleanrooms capture and control particles including biological agents with HEPA filters. With proper maintenance most of these filtration based devices can last five to ten years between filter changes.
Chemical fume hoods use airflow to capture, dilute and expel hazardous gases and fumes from the laboratory or work area. Chemical fume hoods tend to be simpler in construction and do not have internal fans or filters. The major cost is heating, cooling and conditioning the air required to replace the expelled air. Mills and Sartor estimated the annual cost of external exhaust at $4.50 per cfm per year. A typical fume hood with an opening 3 ft wide and 18 inches tall would require approximately 450 cfm and cost over $2000 per year in energy.
If biological containment or protection is required, then filtered equipment is necessary. If the containment or protection required is from volatile chemicals or gas, then externally exhausted equipment is necessary.
From a cost standpoint, the decision that a BSC must provide protection from gases and volatile chemicals in addition to biological hazards increases the overall cost of the BSC significantly. For safety and efficiency, it becomes vital to determine precisely what type of protection is needed. Table 1 provides a rough comparison of total costs in energy and upkeep for the three types of containment equipment discussed. Note how the decision to provide protectio n from both biological hazards and volatile toxic chemicals more than doubles the total cost of operating the BSC.
Strategy Two: Not All BSC Users Are The Same
With the exception of external exhaust, the major ongoing costs of a Class II BSC are associated with use. When the cabinet is operating; the fans are spinning, the fluorescent lights are on, the filters are loading up with captured particles and motors are wearing down. None of this happens when the cabinet is completely off.
Some BSCs are used only occasionally when only some of the work requires the cleanliness and containment of a BSC, and turned off when they are not in use. Other BSCs are always in use, particularly if they are connected to external exhaust systems where air is constantly flowing through the cabinet.
Table 2 shows a comparison for total costs in energy and upkeep for three different types of use of a traditional BSC. These costs will vary with the energy and operational efficiency of the particular model of BSC.
A part of an overall strategy to maximize the cleanliness and containment provided by a facility’s BSCs while optimizing the costs requires recognition that the usage and costs can vary significantly. Some energy efficient BSCs available today operate at 75% lower levels than popular and much more inefficient models common in the past. The heaviest users should have the most efficient cabinets for the maximum reduction in a facility’s overall costs.
Strategy Three: Timing is Everything.
The costs of operating a BSC are not evenly distributed over the 15 or 20 years of the BSC’s life. In the first year, the only costs will be for electricity and cooling. At some point the filters and/or motors will need replacement. The cost for this will be between $1,000 and $2,000 or even more. For the traditional BSC, filters and motor replacement are approximately 35% of the total cost of operation over 15 years.
Table 3 shows the typical pattern of expenditure for a BSC power user. Note the annual expenses are the same from year to year unless the filters need to be replaced as in years seven and fourteen or the motor needs replaced as in year ten. Newer BSC technologies further improve the TCO model due to longer filter and motor life. Replacing a BSC rather than spending the money to replace significant components may be the most cost effective way to transition from a costly inefficient BSC to a more cost effective BSC.
Putting it Together
These strategies can be implemented as part of an overall approach using these steps:
- Conduct a BSC inventory survey with guidance from Thermo Scientific.
- Identify the top 20% in terms of operating cost
- Review application requirements with environmental health and safety.
- Identify cost/benefit for unit replacement
- Identify cost/benefit for timed unit replacement.