Q. It appears that the ANSI/ASHRAE Standard 62.1-2010 restricts the use of wheels for lab use. Is this the correct interpretation?
A. As it stands ANSI/ASHRAE Standard 62.1-2010 is not clear on the question of Class 4 exhaust (which includes lab fume hood exhaust). The standard reads as follows:
18.104.22.168.2 Class 3 air shall not be recirculated or transferred to any other space.
Exception: When using any energy recover device, recirculation from leakage, carryover, or transfer from the exhaust side of the energy recovery device is permitted. Recirculated Class 3 air shall not exceed 5% of the outdoor air intake flow.
22.214.171.124 Class 4 Air. Class 4 air shall not be recirculated or transferred to any other space nor recirculated within the space of origin.
Since there are no exceptions listed for Class 4 air this can be interpreted to mean that absolutely no cross airflow is allowed and would in turn not allow the use of total energy recovery devices serving laboratory fume hoods.
Help is on the way. In February Ashrae published Proposed Addendum k to Standard 62.1-2010. It is now in final review and comment stages. This proposed addendum adds an exception to the recirculation limits on Class 4 exhaust air streams from laboratory hoods which would allow use of heat wheel energy recovery in some cases. The exception defines several criteria which the airstream must meet before such heat recovery can be used, and the heat recovery system must limit recirculation airflow to less than 0.5% of the outdoor air intake flow.
Addendum k to 62.1-2010 – proposed to revise Section 126.96.36.199 as follows:
Section 188.8.131.52 Class 4 Air. Class 4 air shall not be recirculated or transferred to any space nor recirculated within the space of origin.
Exception: When using any energy recovery device, recirculation from leakage, carryover, or transfer from the exhaust side of the energy recovery device is permitted subject to the following restrictions:
a. Laboratory exhaust from facilities where the use of chemicals is related to testing, analysis, teaching, research or developmental activities and where chemicals are used or synthesized on a nonproduction basis, rather than in a manufacturing process, provided that:
1. The laboratory is classified as BSL 2 or lower,
2. The exhaust air from a BSL 3 laboratory has been HEPA filtered prior to entry into the heat recovery system,
3. The laboratory does not handle explosive or reactive chemicals that could accumulate or react on or within the heat recovery system, and
4. The mass balance calculations specified in the IAQP shall be used with the emissions to be handled by the exhaust system to ensure that resulting concentrations in the space are below acceptable limits, such as those specified in Appendix B.
b. Recirculated Class 4 air shall not exceed 0.5% of the outdoor air intake flow.
Further questions on Energy Recovery Wheels; askRick?
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Ask Rick: Energy Recovery Wheels on Laboratory Fume Hood Exhaust?
Ask Rick: How much cross contamination occurs with an Energy Recovery Wheel?