The new edition of this national code was published in 1988. It touched off waves of deep concern on how to handle a major leak and at the same time be within the requirements of the UFC. The basic objective of this code as it pertains to toxic gases is that the neutralizing system must be able to handle any "worst-case" type of leak so that the fire-fighters will never have to be required to enter the facility.

In Section 80.303, page 332, it states: "Such exhaust systems shall be capable of diluting, absorbing, neutralizing, burning or otherwise processing the entire contents of the largest single tank or cylinder of gas stored."

On p.333, it says that: "For portable tanks and cylinders, the maximum flow rate of release shall be calculated based on assuming the total release from cylinder or tank within the time specified in Table No. 80.303-B." For liquid chlorine release the table specifies 30 minutes for chlorine cylinders and 240 minutes for portable tank. Then on page 333 it says further that: "When portable tanks or cylinders are equipped with approved excess flow or reduced valves, the worst case release will be determined by the maximum achievable flow from the valve as determined by the valve manufacturer or the gas supplier."

These statements mean that the scrubber system would have to be able to handle the entire contents of a ton cylinder in 30 minutes and a 25- or 35-ton tank in 240 minutes. This will require a scrubber capacity of 67 lb/min for a ton cylinder and 208 lb/min for a 25- or 35-ton tank. These tanks are usually equipped with 14,000 lb/hr excess flow valves. In spite of the fact that 4000 lb/hr flow valves are not currently available, they should be put on 25-and 35-ton tanks. This calculates to 96,000 lb/day chlorine capacity, which is more than ample for this tank size. For larger tanks, 7000 lb/hr flow valves should be used instead of the 14,000 lb/day valves. The 7000 lb/day valves are currently available.

If the 25- or 35- ton tanks were equipped with 4000 lb/hr excess flow valves, then the scrubber system would only have to handle 67 lb/min -the same as that of a ton container.