Okla. Stat. tit. 52, § 52-296.1: Securing of crude oil storage tanks

The owner or operator who owns or has control over a production

crude oil storage tank shall be required to do one of the following:

1. Install and maintain a locking or sealing device on the

thief hatch of the tank;

2. Reduce the opening of the thief hatch to not greater than

six (6) inches in diameter; or

3. Affix and maintain a sign on or near the thief hatch which

shall meet the following specifications:

a. the size of the sign shall be no smaller than forty

(40) square inches,

b. the sign shall read "DANGER DO NOT OPEN", and

c. the word "DANGER" on the sign shall be no smaller than

two (2) inches and the words "DO NOT OPEN" shall be no

smaller than one (1) inch.