Biosafety Level 3 (BSL3/CL3) Laboratory Solutions

The Celeris® critical environmental control platform from Phoenix Controls is designed to provide unmatched airflow and space comfort control for today’s demanding high-level containment level 3 (BSL3/CL3) facilities. Precision, pressure independent airflow control devices like the Phoenix Controls Accel® II venturi valve, coupled with the highly configurable, Celeris control platform using either volumetric offset or Progressive Offset Control (POC) is the logical choice in these high performance, high risk applications.

 

Biosafety Level 3 laboratories (BSL3/CL3) and also biosafety level 2 research suites often consist of multiple interdependent spaces where air change rates are typically high while offset or leakage airflow is extremely low due the architectural tightness of these spaces. In these applications pressure control zones are cascaded one on top of another to provide multiple containment barriers between the research space and public corridors. Access control and door interlocks are also often required.

While many of these applications reliably operate using volumetric offset control, some designs require active space pressurization control. To address this need, Phoenix Controls developed the progressive offset control function which layers a pressure control loop over top of the conventional Celeris volumetric offset control. A base offset establishes a positive or negative space then the volumetric control responds to dynamic flow changes within the lab. The pressure control loop then makes finite adjustments to the offset in order to achieve the precision of control and responsiveness required. Spaces controlled with the POC function generally exhibit superior performance over conventional pressure control schemes relative to:

  • Closeness of control

  • Responsiveness to changes in switched or variable airflow control devices

  • Recovery from a disturbance, such as a door opening or closing

The superior performance of the POC function is attributed to the Celeris high-speed volumetric offset control function, which controls gross changes in airflow, and includes:

  • Base ventilation demand (air changes)

  • Base pressurization levels

  • Thermal override for cooling or heating demand

  • Monitoring flow feedback of non-networked switched or variable flow devices, such as biosafety cabinets and dust collectors, and responding to changes in flow

The subtle tuning in pressurization control is handled through an independent control loop layered over the top of the volumetric offset control function. A relatively small percentage of the total flow control range is reserved for pressurization control.

  • This provides greater accuracy and resolution because the pressure control loop is operating over a small percentage of total flow.

  • Even with the pressure control loop disabled, there is still volumetric offset and directional airflow control.

The POC function responds quickly to maintain directional airflow when a door to the pressurized space opens and recovers quickly once the door closes. Because it is not practical to maintain space pressurization across an open door, door switches are used to detect the opening or closing of doors to adjoining spaces. This method allows the system to:

  • Freeze the pressure control loop to prevent it from winding up

  • Freeze the pressure control output at the last value

  • Change the offset to a higher value while the door is open to increase the directional airflow, which prevents space contamination

Shut-off valves

Phoenix Controls Shut-off Valves are available in two designs: standard and low leakage. The Shut-off valve combines a precision, pressure independent airflow control device and a shut-off device in one package which may be controlled locally, over the network—either from the building management system (BMS) or Local Display Unit (LDU), or as part of a room-level control function.

  • Under normal operation, a Shut-off Valve provides the critical airflow control performance demanded by a modern research facility.

  • In the shut-off mode, it closes to provide isolation of the HVAC system from the space under control.

Both configurations of the Shut-off valve include design features that significantly reduce casing leakage to approximately 0.03 cfm per square foot of area at 30 inches of static pressure (0.15 l/s per square meter). Available with either standard or high-speed electric actuation, response time from control to closed is typically less then 60 seconds, and 1 second respectively.

 

Standard Shut-off

The standard Shut-off valve relies on a metal on metal seal which allows leakage on the order of 5 cfm (8 ¼ M3H) at 5 in. W.C. Typical applications include gaseous biodecontamination, GEX shut-off, fume hood decommissioning, or lab decommissioning.

 

Low leakage Shut-off

The low leakage design adds a gasket that provides near bubble-tight shut-off performance at a fraction of the cost. Leakage rates approach 0.02 cfm at 30 in. W.C. (0.0092 l/s at 7,500 pascals) and has been tested with ASME N510s pressure decay method and meets the following leakage standards:

  • European Committee of Air Handling and Refrigeration Equipment Manufacturers (EUROVENT), sections 2.2 and 2.3 of EUROVENT WG 6B

  • U.S. Department of Energy (DOE), Nuclear Air Cleaning Handbook

  • Public Health Agency of Canada, Laboratory Biosafety Guidelines

Typical applications might be to isolate a space for decontamination and Biosafety Level 3 laboratories (BSL3/CSL3) applications where near bubble-tight shut-off meets the safety and containment requirements.

The standard shut-off valve provides sufficient isolation for gaseous decontamination while the lower leakage shut-off valve satisfies most requirements where bubble-tight dampers have typically been applied.​