HOUSTON, Texas (KTRK) -- Citing threats to first responders' safety, the Houston Police Department and Harris County Sheriff's Office will no longer perform drug tests in the field, the departments announced Friday.The policy change takes effect at midnight on Saturday, July 15."The last thing we want to do is end up in the hospital in the middle of the night or, God forbid, having to knock on the door because their loved one has died as a result of these extremely dangerous jobs," Houston Police Chief Art Acevedo said, citing a recent example in which a local deputy was inadvertently exposed to lethal amounts of carfentanil during an investigation.Although that deputy survived, it took six doses of overdose reversal drug Narcan to get him "back on the path to good health," Acevedo said.The Harris County Sheriff's Office has also ordered several hundred doses of Narcan to protect first responders in the field, Capt. Rolf Nelson added.Paul Fortenberry from the District Attorney's Office said Harris County authorities had seized 11 kilograms of fentanyl in the last 60 days."It's fair to say that words do not give it justice. It's an extremely dangerous substance," Fortenberry said. "There have been cases where officers are on the side of the road and they merely opened up a bag to field test it and the action of closing the bag forced up enough air containing the substance that it sent the officer into overdose mode."In 2016, the DEA issued a warning to law enforcement agencies advising of the threat of synthetic opioids like carfentanil, which is 10,000 times more potent than morphine."Improper handling of carfentanil, as well as fentanyl and other fentanyl-related compounds, has deadly consequences," the agency advised.Several other law enforcement agencies around the country, including the Pasadena Police Department, have announced similar policy changes.