The average portable toilet contains a 50-60 gallon holding tank that will fill up after about 75 uses. We usually recommend that you rent one toilet for every 8 to 10 people you expect at an event. For longer term rentals such as at a construction site, we recommend the same ratio during an 8 hour day and that the toilets be pumped and serviced once every two weeks.
The National Fire Protection Agency (NFPA) guidelines say that you should clean your kitchen exhaust system every six months if your establishment uses a fryer or grill. Most insurance companies follow this guideline and require cleaning to take place at a minimum of every six months to keep the insurance policy in force. Check with your city requirements, since they may require more frequent cleanings.