Ventilation for Science Lab.

[Newnorthman]

In school science labs chemicals are stored for use in later school activities. What are the requirements for ventilating the chemical storage room. We have an acid storage cabinet, a flammable storage cabinet, and nitric acid stored in a container in a wooden cupboard. We can vent all the cabinets directly to the room and then exhaust the room or we can exhaust each of the cabinets separately directly to outside. The amounts of chemicals are small possibly largest being 5 liters.
What is best solution for venting the room. Does the fan and electrical in room need to be explosion proof.?

 

[SAK9]

Generally lab solvants are stored in vented cabinets.The cabinets have ventilation slots at the bottom.The top side of the cabinet is connected to the lab exhaust duct.Incafe of flammable solvents it is recommended to have flame proof motors or have the motors outside of the air stream as in a centrifugal fan

 

[ChasBean1]

Below is courtesy of NFPA-30.

4.3.4.4.2* Ventilation requirements shall be confirmed by one of the following procedures:
(1) Calculations based on the anticipated fugitive emissions. (See Annex F for calculation methods.)
(2) Sampling of the actual vapor concentration under normal operating conditions. The sampling shall be conducted at a distance of 1.5 m (5 ft) radius from each potential vapor source extending to or toward the bottom and the top of the enclosed storage area. The vapor concentration used to determine the required ventilation rate shall be the highest measured concentration during the sampling procedure.
(3) Ventilation at a rate of not less than 0.3 m3/min of exhaust air for each m2 of solid floor area (1 cfm/ft2).

 

[ChrisConley]

Just to comment on the 'fan and motor' being explosion proof. Motor's can come explosion proof, although it is usually easier to move the motor out of the air stream. Fans can never be explosion proof; they are instead selected to be 'spark-resistant'. Spark resistance is created by reducing the chance of ferrous components coming into violent contact. This is done by replacing some or all of the parts in the fan with aluminum or FRP AMCA has three ratings A, B and C. Spark resistance increase from C to A. For a high school science lab I think an AMCA rating of C would be adequate.

 

[SlipMatWax]

You will need a fan with an aluminum wheel and a non-ferous rub-ring for the shaft opening into the fan scroll. (Type C)