Cal. Code Regs. tit. 19 § 1300
Before applying any flame-retardant chemical, the application concern shall first carefully examine the fabric or material to determine:
Assuming that the fabric or material is of a type for which the chemical has been registered, the concern must then decide how much chemical must be applied. This will depend on the area to be treated and the type of fabric. The percent weight gain must be commensurate with that determined for the chemical on the standard qualifying fabric. It may be necessary to apply slightly more or less chemical than this, depending on the weight and type of the particular fabric being treated, but in every case sufficient chemical shall be applied to obtain satisfactory flame resistance.
If examination shows that the fabric has been previously treated, consideration must be given to the possibility that the old treatment combined with the new might nullify the flame-retardant effect, or might cause excessively rapid deterioration of the fabric. Whenever possible, all traces of any previous chemical treatment should be removed before re-treating.
The presence of sizing in a fabric can have a decided effect on the flame-retardant treatment, especially the exterior type. Some exterior chemicals will be registered only for the treatment of unsized or desized canvas, and may not be applied to a sized material unless the sizing is first removed. Whenever practical, sizing should be removed before treatment with any chemical, since a treatment is always more effective and will last longer on an unsized fabric.
Celanese and acetate type rayons are extremely difficult to treat successfully, even though chemicals may be listed as approved for such fabrics. Applicators are cautioned not to undertake the treatment of such fabrics unless they have adequate knowledge and experience.
Before treatment of printed or dyed interior fabrics, the applicator must determine if the colors are fugitive and apt to run if the fabric is wet. In such a case, the applicator must be especially careful in applying the chemical, so as not to cause the colors to run.
It is an acknowledged fact that certain metals and metallic pigments in contact with chlorinated paraffin will accelerate the liberation of hydrogen chloride, especially at high temperatures. This effect is most pronounced with iron, zinc, and pigments composed mainly of salts of these two elements. Zinc oxide is extremely harmful in this respect and its use should be avoided, since its effect extends even to properly stabilized chlorinated paraffins.
Cal. Code Regs. Tit. 19, § 1300