Date: Fri, 19 May 2006 14:40:07 -0400
Reply-To: rentasc**At_Symbol_Here**NCC.EDU
Sender: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
From: rentasc**At_Symbol_Here**NCC.EDU
Subject: Ventilation of Chemical Storage Cabinets Response to question
from Yung Morgan

Hello All:

I am posting below the document on venting of cabinets for the benefit of others who may be interested in this topic.


Venting of Storage Cabinets
NCC Chemical Hygiene Plan – 2005 Edition
Chemical storage cabinets, whether used for flammables, corrosives or pesticides/poisons, often come with capped bung openings that allow ventilation. Ventilation of corrosive cabinets may be necessary in some indoor applications for the release of potentially toxic vapors and gases, and to prevent corrosion. Ventilation of pesticides/poisons cabinets to the outdoors is not recommended due to potential environmental health hazards. Ventilation of flammable cabinets may be necessary in some applications to release potentially explosive or hazardous vapors and to prevent backflash into the cabinet. While cabinet manufacturers provide the bungs for venting, ventilation for chemical storage cabinets is NOT required or even recommended by any Federal regulatory agency. Cabinet manufacturers include venting bungs for users who want to vent for safety and health reasons, or for users who are required to vent by state or local codes, or by individual company or insurance carrier pol
Don’t Vent Unless You Have To.

According to NFPA (National Fire Protection Association) Code 30, Flammable and Combustible Liquids Code Handbook, venting a chemical storage cabinet is not necessary for fire protection purposes. Flammable and combustible liquid storage cabinets are designed to protect the internal contents from a fire outside the cabinet. A vented cabinet could compromise the ability of the cabinet to protect its contents from a fire.

According to NFPA Code 30, 4-3.2, “The cabinet is not required to be vented for fire protection purposes. However, the following shall apply: 

(a)If vented for whatever reasons, the cabinet shall be vented outdoors in such a manner that will not compromise the specific performance of the cabinet, as acceptable to the authority having jurisdiction. 

(b)If the cabinet is not vented, the vent openings shall be sealed with the bungs supplied or with bungs specified by the manufacturer.” 

NFPA 30 clearly dismisses the need to vent storage cabinets in its appendix. Under A-4-3.2 it states, “Venting of storage cabinets has not been demonstrated to be necessary for fire protection purposes. Additionally, venting a cabinet could compromise the ability of the cabinet to adequately protect its contents from involvement in a fire since cabinets are not generally tested with venting. Therefore, venting of a storage cabinet is not recommended.” 

Federal OSHA recognizes the NFPA guidelines when it comes to chemical storage cabinets, so there’s no requirement to vent cabinets for OSHA compliance. However, this does not mean it is not required in some circumstances. State and local authorities having jurisdiction (AHJ) may require venting. NFPA 30 acknowledges this later in A-4-3.2. stating, “However, it is recognized that some jurisdictions may require storage cabinets to be vented and that venting may also be desirable for other reasons, such as health and safety. In such cases, the venting system should be installed so as to not affect substantially the desired performance of the cabinet during a fire. Means of accomplishing this may include thermally actuated dampers on the vent openings or sufficiently insulating the vent piping system to prevent the internal temperature of the cabinet from rising above that specified. Any make-up air to the cabinet should also be arranged in a similar manner. If vented, the cabin
et should be vented from the bottom with make-up air supplied to the top. Also, mechanical exhaust ventilation is preferred and should comply with NFPA, Standard for Installation of Blower and Exhaust Systems for Dust, Stock, and Vapor Removal or Conveying. Manifolding the vents of multiple storage cabinets should be avoided.” 

How Do I Know If I Need To Vent My Cabinet 

In addition to acknowledging that the local AHJ requirements supersedes that of the NFPA, the above appendix passage identifies that venting is occasionally necessary and how it can be achieved. 

The following five steps help to determine whether or not to vent a chemical storage cabinet: 

1.	Determine Classification (Flammable, Corrosive and Oxidizer), health hazards, storage requirements (i.e. temperature, incompatibilities) and total amounts of the chemicals that will be stored in the cabinet. Refer to the Material Safety Data Sheets (MSDS) for this information or contact the manufacturer/supplier for assistance. This information may be needed for the following steps.

2.	Contact your local Fire Marshal/Fire Inspector to determine if venting is required by your local or state regulations. If so, obtain their instructions and any other special requirements.

3.	Contact your Environmental Health and Safety (EHS) Officer, if applicable. Many companies, universities, school districts and other large facilities have internal requirements for venting storage cabinets. Again, request instructions and special requirements since they may vary.

4.	Consult with your insurance company for their recommendations and requirements.

5.	Have air quality evaluated to determine actual explosive limit value in and around the storage area. Consult an Industrial Hygienist for assistance. Your State OSHA Consultation Office will either provide you with an accredited hygienist that is on-staff, or will help you contact one in your area. 
If the cabinet’s contents are creating excessive levels of chemical vapors, it doesn’t necessarily mean the cabinet must be vented. Before venting a cabinet to lower vapor emissions, consider the following options: 

1.	Place cabinets in a cool, dry location out of direct sunlight and away from any possible heat or ignition source. Temperature fluctuation in many chemicals will increase harmful vapors emitted.
2.	Always maintain continuous and adequate room ventilation. Many accidents occur when ventilation is turned off for the weekend or an extended period of time. 

3.	Maintain an accurate inventory of chemicals and their properties to prevent dangerous reactions resulting from incompatible chemical storage. Never store chemicals solely based on alphabetization, as this can result in dangerous chemical reactions.

4.	Store chemicals only in containers that are made of materials determined to be chemically compatible so that leakage/damage will not occur. Consult the MSDS or manufacturer for their recommendations. Frequently inspect containers for signs of damage and aging. 

5.	Always make sure that caps are replaced on containers tightly, and that the outside of containers is clean and free from residual liquids. 

6.	Regularly inspect inside the cabinet for spills, and clean immediately if found. 

7.	Regularly inspect cabinets and any metal items in surrounding area for signs of rust, corrosion or other visual indications that the vapor levels are excessive and mechanical ventilation would be needed. 

8.	Dispose of any aging chemicals that could become unstable. 

9.	Use of vapor absorbent inside the cabinet can also reduce the irritant level of vapors. 

What If I Have To Vent My Cabinet? 

If a decision is made to vent, follow the engineering guidelines from the AHJ that requires the venting. At the very minimum, venting should incorporate the following steps: 

•	Remove both metal bungs from sides of cabinet and replace flame arrester screens (normally these come with the cabinets) into the openings. 

•	Connect the bottom opening to the exhaust fan using rigid metal tubing equivalent or better than that used in construction of cabinet. Tubing must have an inner diameter no less than that of the opening. Several places require welding of the tubing to the cabinet to avoid riveting or other methods that may impede the cabinet’s fire protection. PVC should not be used since it can not withstand excessive temperatures. 

•	The top opening shall serve as the fresh air inlet. The make-up air should be supplied to the fresh air inlet in tubing similar to that used for the exhaust. 

•	A suitable fan should be constructed of non-sparking blades and shrouds. Mechanical exhaust ventilation is preferred and should also comply with NFPA 91 Standard for Exhaust Systems for Air Conveying of Vapors, Gases, Mists and Noncompatible Particulate Solids. 

•	The total run of the exhaust duct should not exceed 25 feet. 

•	DO NOT manifold vents of multiple cabinets—in many localities it is prohibited. 
While the above guidelines refer most specifically to flammable liquid storage cabinets, they can be modified slightly for use on corrosive or pesticide/poison storage cabinets. Again, the AHJ that requires the venting needs to be consulted for engineering guidance to ensure their specific venting protocol is met. A couple important points to remember are corrosive cabinets require blowers that are chemically compatible with the vapors they move, and some pesticide/poison cabinets can not be vented to the outside due to potential health hazards associated with exposures to the vapors. 

Corrosive/Acid Cabinets

There currently are no regulations regarding the construction of corrosive/acid cabinets, however, most manufacturers construct them of either wood or polyethylene and they are usually blue in color. The EPA does require that the cabinets be able to contain any possible spills. Polyethylene is the most common material used for acid/corrosive cabinets. Chemical compatibility is the biggest reason to use this material along with the fact that polyethylene can be welded at the seams to provide better spill protection. Wood can be another choice of material for these cabinets, but chemical handling and storage requirements should be closely evaluated since several acids are incompatible with wood and could ignite if spilled.
Acid/Corrosive cabinets are primarily vented only when required by local authorities or the company. Cabinets made from either wood or polyethylene are normally not provided with bungs. However, some manufacturers will custom make them for those very few areas where venting would be required. Metal cabinets are the final option, and most likely need to be vented to prevent rusting and corrosion. When venting a corrosive cabinet, as opposed to a flammable cabinet, connecting to an existing exhaust such as a fume hood is strongly recommended. Fume hood exhaust systems are designed to handle corrosive vapors. Flame arrestors do not need to be used and PVC is the best material for venting of corrosives. 

Pesticide /Poison Cabinets

There are currently no NFPA regulations for the construction of these cabinets, other than the EPA secondary containment regulations and that the cabinet must be lockable. Cabinets for this category are often constructed to the NFPA 30 standard since more often than not these chemicals will also be flammable. Pesticide cabinets are most often green in color while Poison cabinets are most often white or gray. Venting should be avoided if at all possible. Many pesticides/poisons should not be vented outdoors due to potential health hazards. Again refer to the MSDS and/or manufacturer for storage requirements as well as EPA regulations and restrictions. 

Commonly Asked Questions

Q.	What is a flame arrester?
A.	A flame arrester is a special fine metallic screen that prevents back flow or flashbacks of flames. Designed to allow liquids and vapors to pass through, it provides a barrier to flame passage if the vapors on either side should ignite.

Q.	Do I need separate flammable and combustible cabinets?
A.	No, provided that the total amount stored in the cabinet does not exceed 120 gallons of which only 60 gallons may be from Class I and Class II. Also note that no more than three of these cabinets may be stored in the same fire area unless there is a separation of greater that 100 feet. 

Q.	Do I need self-closing doors?
A.	Self -closing doors are not a NFPA requirement; however, the Uniform Fire Code 66 does require that all flammable cabinets have self-closing doors. Many States and local codes do require compliance with the UFC. To find out if you are in an area with this additional requirement, contact your local Fire Marshall.
Sources for more Information

29 CFR 1910.106 (d)(3)(ii)(a)
EPA Uniform Fire Code 
UFC 66

Carlos Rentas Jr., MA, MPH, CSP, CHMM, CCHO, EMT-D
Director of Safety, Health & Environmental Compliance Programs
Nassau Community College- State University of New York
358 Davis Avenue, 2nd Floor, Rm. 8
Garden City, New York  11530
(516) 572-7781  FAX (516) 572-7841
rentasc**At_Symbol_Here** or crentasjr**At_Symbol_Here**

"Reputation is what other people know about you. Honor is what you know about yourself."  Lois McMaster Bujold 

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