N.Y. Comp. Codes R. & Regs. tit. 6, § 257-3.6 – Sampling frequency.

(a) The following guidelines regarding minimum frequency of sampling shall be used to determine compliance with standards.
1. (1) 24-hour standard—every sixth day sampling—minimum of 50 samples.
2. (2) 30-day standard—every day sampling—minimum of 24 samples.
3. (3) 60-day standard—every other day sampling—minimum of 24 samples.
4. (4) 90-day standard—every other day sampling—minimum of 36 samples.
(b) Suspended particulate standards.