Risk Management & Safety Department – Health & Safety – Laboratory Chemical Safety

Fume Hood Exhaust System Maintenance –
Cooperation is Needed for Everyone's Safety

The General Problem:
Fume hood exhaust systems must receive periodic preventive maintenance to minimize equipment failure and emergency shutdowns. Fume hood exhaust fans must be turned off to perform this periodic maintenance activity. Turning off fume hood exhaust systems presents a potential chemical exposure hazard for both lab occupants and any maintenance personnel who might be on the roof.

The Basic Function of Fume Hood Exhaust Systems:
Fume hoods are one means of working safely with volatile hazardous or odorous chemicals (gases, vapors, dusts, mists, fumes, etc.).

The exhaust air creates a capture velocity at the face of the fume hood that prevents hazardous or odorous chemicals from escaping into the lab.
Airflow through the exhaust system dilutes hazardous or odorous chemicals.
The exhaust discharge stack on the roof disperses and further dilutes hazardous or odorous chemicals into the atmosphere.

When Fume Hood Exhaust Systems Are Turned Off:

The fume hood capture velocity is not sufficient to contain volatile hazardous or odorous chemicals. Lab personnel can be exposed to the chemicals if in use.
The positive pressure of the building (caused by the building's operational air supply) pushes volatile hazardous chemicals out the roof stacks at low velocity. Thus, dilution of hazardous chemicals in the exhaust is significantly lessened (i.e., higher hazardous chemical concentrations in exhaust).
Also, lower velocity exhaust stack discharge means less dilution in the atmosphere and higher hazardous chemical concentrations at the roof where maintenance personnel may be working.

The General Solution:

Facilities Management (FM) must notify lab personnel about fume hood exhaust system preventive maintenance shutdowns.
Lab personnel must not use fume hoods during fume hood shutdowns.

Specific Solution: Hood Exhaust Fan Shutdown Procedure

Step 1. Establish Maintenance Schedule
FM must establish an agreed upon quarterly routine maintenance schedule with the building occupant representatives (e.g., building managers). This will provide a consistent date for subsequent years so that FM can schedule work in advance and lab personnel can plan their work around the schedule.

Step 2. Notification of Upcoming Work
FM must provide a written notification to the building list (i.e., list, developed by and submitted to FM by building managers and department heads, of individuals they would like FM to notify by e-mail) prior to scheduled maintenance. Those on the building list must in turn notify lab personnel about the shutdown and their responsibilities (see below).

The FM notification instructs lab personnel to:

SHUTDOWN ALL PROCESSES AND DISCONTINUE ALL ACTIVITIES IN THE FUME HOODS, and
CONTAIN OR REMOVE ALL HAZARDOUS MATERIALS prior to the maintenance, and
DO NOT USE THE FUME HOODS during the maintenance period.

Step 3. Maintenance
On the day of the work, FM must placard the fume hoods with RED out-of-service signs indicating DANGER – Fume Hoods Shutdown, Do Not Use, and the time and date of the scheduled shutdown. Some hoods will also have the sashes locked down.

FM will verify that all chemicals are either capped or removed and that the hoods are not in use. Maintenance will not proceed unless this is the case.

FM must ensure that all necessary items needed for maintenance are available and on hand before beginning – to minimize fume hood down time.

Step 4. Notification of Completion
FM must notify the lab occupants when work is complete and the exhaust systems are operating normally, by removing the RED out-of-service signs and unlocking any sashes that are locked down. Lab occupants must not use the hoods until this occurs.

Responsibility Recap:
Facilities Management:

Establish a routine fume hood maintenance schedule with occupants.
Notify the building list when fume hoods will be shutdown.
Lock down sashes and/or placard fume hoods with RED out-of-service signs just before the shutdown.
Verify lab personnel fulfill their responsibilities (see below).
Perform maintenance in a timely manner.
Unlock sashes and/or remove the RED out-of-service signs when maintenance is complete and hoods are operational.

Building Managers:

Notify lab personnel of upcoming shutdowns and their responsibilities.

Lab Personnel: Before the scheduled shutdown:

SHUTDOWN ALL PROCESSES AND DISCONTINUE ALL ACTIVITIES
CONTAIN OR REMOVE ALL HAZARDOUS MATERIALS.
DO NOT USE THE HOODS until the sash locks and/or RED out-of-service signs are removed.

Fume Hood Exhaust System Maintenance – Cooperation is Needed for Everyone's Safety

Fume Hood Exhaust System Maintenance –
Cooperation is Needed for Everyone's Safety