So what kind of sunglass do we have, metal frames and glass lenses, metal frame with plastic lenses, all plastic both frame and lenses, cheap Walmart type or expensive $200 pair? This will all drive the final commodity. BUT how sure are you they all are class IV, how many pallet loads can be group A plastic before it becomes a problem? Well take a look at what NFPA 13 says about this below for mixed commodities.
As you can see below 10 pallet loads of a higher commodity is permitted in a 40,000 sq.ft. warehouse. That is NOT a lot, it also says they can not be near each other. It does not take much for the fire to take hold if the design is not correct. Based on full scale testing they found it only takes a single pallet load in a fire to overcome the sprinkler density and not control a fire.
So why did I go with Group A Plastic because I have been down this road way too many times. Products change and sprinkler designs do not. I work for an insurance company with a large engineering staff. We find about 50% of the warehouses we evaluate the sprinkler design is not correct. So that is why I said Grp A.
Remember the answer is not as simple as what the code says, sometimes you have to use judgement and experience. Many new warehouses have gone to ESFR sprinklers with the hope it would solve all problems with commodity classification and inadequate sprinkler protection. Unfortunately ESFR has it's own problems and is not a one size fits all approach.
5.6.1.2 Mixed Commodities.
5.6.1.2.1 Protection requirements shall not be based on the
overall commodity mix in a fire area.
5.6.1.2.2 Unless the requirements of 5.6.1.2.3 or 5.6.1.2.4 are met, mixed commodity storage shall be protected by the requirements for the highest classified commodity and storage arrangement.
5.6.1.2.3 The protection requirements for the lower commodity class shall be permitted to be utilized where all of the following are met:
(1) Up to 10 pallet loads of a higher hazard commodity, as described in 5.6.3 and 5.6.4, shall be permitted to be present in an area not exceeding 40,000 ft2 (3716 m2).
(2) The higher hazard commodity shall be randomly dis- persed with no adjacent loads in any direction (including diagonally).
(3) Where the ceiling protection is based on Class I or Class II commodities, the allowable number of pallet loads for Class IV or Group A plastics shall be reduced to five.