Control Banding Handout

Laboratory Ventilation “Control Banding”

“Control Banding” is a system for assigning generic protection strategies to similar hazards based on a risk assessment of specific instances of those hazards; the hazards are grouped into “bands” that can be managed by the same suite of controls. The control banding strategy was developed by industrial hygienists to identify control methods to deal with situations in which hazard information is limited, or the hazards of concern change regularly i, ii. In the chemical laboratory setting, general dilution ventilation of laboratories, beyond that recommended by the American Society of Heating, Refrigerating and Air-Conditioning Engineers ASHRAE 62 standard, is a core engineering control of occupant chemical exposures during normal operations. For this reason, specification of general ventilation rates in laboratories should be based on a risk assessment of the hazards associated with the use of volatile chemicals in the laboratory.

In order to assure the operational, financial and environmental flexibility, and sustainability of laboratory operations, these ventilation rates should be minimized as much as possible. Over-ventilation of laboratory spaces can interfere with the use of the laboratory for specific operations; can make the detection and diagnosis of operational and ventilation problems in the laboratory more difficult; and increases the carbon impacts and dollar costs of operating the laboratory facility.

Balancing these factors in an ongoing way that is accessible to a variety of stakeholders is the key goal of the Laboratory Ventilation Standard developed by the American Industrial Hygiene Association (ANSI Z9.5-2012)iii.  This standard requires a procedure for characterizing hazardous processes in the laboratory.  ASHRAE's guidance document Classification of Laboratory Ventilation Design Levels details considerations for the design of ventilation systems of new laboratories iv.
The optimization process consists of review of laboratory chemical uses to determine whether they require high, medium, or specialized general ventilation.

High ventilation:

Laboratories in which there are significant volatile chemical or specific process hazards for which employee exposures are expected to be controlled by the general ventilation system are designated for ventilation at 8 air changes per hour when the laboratories are occupied and 4 air changes per hour (ACH) when the labs are unoccupied.

This recommendation relies on the expectation that significant point sources of volatile chemicals are contained by effective local exhaust, in the form of a fume hood, local point exhaust, or an appropriate chemical storage cabinet. For this reason, in these control bands laboratory workers will be trained in best practices for using ventilation systems in the laboratory, specifically in the proper use of the specific fume hood models and control systems provided in their laboratory and the process of deciding which processes should be located in a fume hood based on risk criteria.  Specific chemical classes that require this level of ventilation are those used in concentrations and quantities sufficient to create significant volatility hazards. In general, chemicals which have “Danger” designations in the Globally Harmonized System (GHS)v based on their volatility and for which dilution is an acceptable control strategy should be considered for this control band. Specifically, these chemicals have GHS P-codes of P260 and P271vi.

Moderate ventilation:

In many cases, where use of volatile chemicals are more limited, the specified ventilation rates can be lowered to 6 ACH occupied / 3 ACH unoccupied. In these cases, worker education about laboratory ventilation can be more generic and simplified.

Specific chemical classes that require this level of ventilation are those that are used in concentrations and quantities that can create odors and nuisances. These chemicals generally have “Warning” designations in the GHS system based on their volatility; specifically these chemicals have GHS P-codes of P261.

Low ventilation:

In the lowest hazard control band are laboratories where the chemicals used are minimal and ventilation requirements can be lowered to those required to support air exhaust from the space, temperature and human occupancy needs for the room. It should be noted that such rooms may have other hazards, such as lasers, welding fumes or significant heat sources which may drive risk-based ventilation needs. One potential strategy is to manage these occasional or discrete chemical risks with local exhaust ventilation rather than general ventilation. Provision of portable exhaust systems with HEPA and/or carbon filters could potentially allow reduction of general ventilation rate in these situations. The ACGIH’s Industrial Ventilationvii manual can be consulted for information about the design criteria of such systems. Depending on the contaminants expected to be used in the room, air exhausted may or may not be of an appropriate quality to be returned to occupied spaces; determinations in this regard should be made on a case by case basis and include chemical spill scenarios when these determinations are made. In any case, chemical use is not the driving factor in ventilation rates, so there is no generic ventilation rate associated with this band; rather specific engineering review based on the actual use of the room is required.

Chemicals appropriate for use in rooms with this level of ventilation are those that have no hazard designations in the GHS system based on their volatility or are used in concentrations or quantities that create no significant volatility hazard.

Laboratory situations that may allow a lower level of air exchanges that require specific review include temperature control rooms, class laboratories whose occupancy periods are well defined, and storage rooms for non-volatile chemicals.

Specific ventilation design required:

Some specific laboratory uses of chemicals may require higher or lower ventilation rates than those generically described above due to specific hazards or requirements that arise from the processes conducted in the laboratory. Assignment of ventilation requirements for these situations lies outside the scope of the generic control banding process and requires specific analysis to determine ventilation needs. Such analysis will be documented by a “basis of operation” report outlining the considerations used in defining the ventilation parameters. This analysis will be supported by development of specific training programs to assure that laboratory workers understand the assumptions and operation of the Laboratory ventilation system.

Examples of chemicals that require a higher level of air exchanges than the 8/4 band are those that have “Danger” designations in the GHS system based on their corrosivity or reactivity in air include animal use areas, semi-conductor processing facilities, glass cleaning rooms without local exhaust ventilation, or areas where non-chemical hazards are present.

This rating system is based on the chemical usage and housekeeping of individual spaces. It is used to indicate the potential for excessive ventilation for a particular lab and is based on the higher rating of the general and local exhaust scores. In operation, these general ventilation rates are sometimes overridden by exhaust and temperature requirements and therefore this ranking represents the best ventilation performance expected.

References

i NIOSH Workplace Safety & Health Topics
ii COSHH Essentials
iii ANSI Z9.5 Laboratory Ventilation
iv Classification of Laboratory Ventilation Design Levels
v See, for example, A Guide to the Globally Harmonized System of Classification and Labeling of Chemicals (GHS)
vi GHS precautionary statements http://en.wikipedia.org/wiki/GHS_precautionary_statements
vii ACGIH, Industrial Ventilation: A Manual of Recommended Practice for Design