Concentrations above 5ppm in air can cause serious problems. You might want to look at this paper, if only to see that, commercially, HCl solutions have another name which can be misleading, Muriatic Acid. What happens if muriatic acid fumes are inhaled?
Answer: A palapa is a thatched-roof, open-sided structure (see palapa photo). The material to cover the roof of a palapa typically consists of dried and woven palm-tree leaves. A palapa is sometimes referred to as a grass or tiki hut.
Example: If the measurement from the top center peak (so you will be measuring half of a circle at a angle) is 4ft to the outer edge of the frame, times that by two which is 8ft then you would order a 9ft palapa umbrella top cover. This will give plenty of overhang around the umbrella edges.