Hello and thank you for coming to Just Answer. We appreciate the opportunity to help you with your questions. Sorry about changing your question format from chat to Q&A, but my computer doesn't deal well with the chat format.
Part of one of my previous jobs was the proper storage of chemicals with all types of dangers. OSHA regulates the storage of flammable material in businesses based on
OSHA standard 29 CFR 1910.106 - Flammable and Combustible
Liquids, which is based upon the 1969 version of NFPA 30 Flammable and
Combustible Liquids Code. OSHA requires that the storage of flammable and combustible liquids meet with the OSHA standard or the most recent NFPA standard.
The National Fire Protection Association (NFPA) sets the national standards for storing all types of chemicals safely, among other fire protection issues. Their website can be found at nfpa.org. NFPA 30 is the standard that you can purchase from the NFPA website that provides all of the code requirements for storing flammable liquids, such as your paint and paint supplies. They sell NFPA 30 for $48.50. If you register for membership with the NFPA at $150 per year, you can also go to the NFPA website, look under "codes and standards", and access the NFPA 30 standard for reading online or printing yourself, as well as other information and advice provided by the NFPA. OSHA standard 29 CFR 1910.106 - Flammable and Combustible Liquids, which is based upon the 1969 version of NFPA 30 Flammable and Combustible Liquids Code can be found here.
The rules and recommendations you will have to follow to store your flammable (paints and solvents) and combustible materials (rags, coveralls, anything made of paper or cloth, generally) depend on the amount of materials you have stored in a single storage area. A single storage area can be your entire warehouse if you have all your materials stored in the open or it can be an UL-approved flammable storage cabinet. If you split up your materials into flammable storage cabinets, you can store more material in your building without needing expensive built-in fire safety systems.
Unfortunately, I would need lots of information about your paints and solvents in storage, how much you store, what combustible materials are present, the sprinkler system and fire control systems built into your warehouse and other information in order to give you specific requirements for your fire protection needs.
Flammable and combustible materials are sorted into a number of categories based on their flash point. The flash point and the classification of your chemicals should be listed on the MSDSs (Material Safety Data Sheets) that you are required to have readily available under OSHA requirements. NFPA 30 lists the classifications of flammable and combustible materials and lists how much of each type of material can be stored in a single storage area. Depending on the amount of paint you store, there are specific requirements for sprinkler systems and the design of your warehouse if you designate the warehouse as one storage area. Based on the classifications and amounts of paint you store, you may find that it is cheaper to purchase flammable storage cabinets and store your materials in a number of storage cabinets (each being its own storage area), than it will be to try to retrofit your warehouse to meet the fire protection code.
OSHA requirements section 1910.106(d)(5)(v) contain the requirements for which would apply to your warehouse if you store your paints and solvents outside of flammable liquid storage cabinets. Our paint storage facility contained hundreds of cans of paint and had sprinklers, raised door thresholds to contain spills, and a six-foot deep tank with a grill to walk on built into the floor to contain spills. The amount of flammable liquids in a warehouse is not restricted as long as the warehouse meets requirements.
I'm sorry that this is much more complicated than the simple recommendations that you requested, but these are the legal requirements that businesses have to follow to be in compliance with OSHA. Your local fire department would be happy to send a fireman over to review your current storage and provide advice on changes you should make to your existing situation, but you have to weigh that easy source of simplified information with the risk that by asking for a fire inspection, your company comes to official notice and you assume liability in the event that you don't implement the recommendations and a fire happens.
I will be happy to continue discussing this question and providing interpretation from the government "legalese" as necessary until you are satisfied with your answer.