This project is a revision of the existing guide for measurements of environmental sensitivities of standard frequency generators. It includes effects and metrology of acceleration; temperature, humidity, and pressure; electrical and magnetic fields; ionizing and particle radiation; and aging, warm-up time and retrace. The purpose is to update effects and metrology of environmental conditions of relevance to frequency generators. The intended audience are manufacturers and users of time and frequency technology. Benefits include information on environmental effects, guide in the measurements of these effects, and aid with the specifications of generators. Revision Standard - Inactive-Reserved. Standard frequency generators that include all atomic frequency standards and precision quartz crystal oscillators are addressed.