When Lieutenant Jason Grogan takes to the road he mentally prepares.

“You start looking how you can serve the community," Grogan said.

But never was his preparation about carbon monoxide until now.

“This is an expense that isn’t that much that we can do to reassure the officers that we’re trying to send them out on the streets to do their job correctly and safely," Grogan said.

Since March, the Modesto Police Department has been testing carbon monoxide detectors.

One is a sticker that turns dark with a positive reading, another is handheld that attaches to the inside of the vehicle.

“We were alerted from other police agencies and watching the news in regard to carbon monoxide and Ford SUV’s and we wanted to take our own precautions," Grogan said.

Grogan is referring to a pair of crashes involving law enforcement agencies in Newport Beach and Austin Texas in which carbon monoxide is suspected of seeping into patrol cars.

Since testing began in March, there have been no true positive readouts in Modesto police vehicles.

The addition of CO detectors, police vehicles also come in the wake of a deadly crash involving a Stanislaus County Sheriffs deputy and Community Service Officer.

Deputy Jason Garner and Officer Raschel Johnson were killed in May.

They died when their Ford Explorer suddenly careened off the road in Modesto out on a burglary call.

The investigation includes testing for carbon monoxide poisoning.

No word yet on results.

Last July, the National Highway Traffic Safety Administration began investigating 154 complaints of exhaust odors entering Ford Explorer model years 2011-2015.

That includes modified Explorers known as Police Interceptor Utilities vehicles.

In a statement, Ford says:

"We take the safety of our customers very seriously and will cooperate with NHTSA on this investigation as we always do. In rare circumstances, there have been instances where customers detected an exhaust odor in Explorers. While it poses no safety risk, customers can and are encouraged to contact their local Ford dealer to address any concerns."

“Just that extra added relief for them to know we are taking care of them," Grogan said referring to other officers.

At roughly a cost of $5,000 for testing and for equipping 24 vehicles with patches and detectors, Modesto is being joined by Turlock and Ceres police, too.

The Stanislaus County Sheriff's Department also began equipping their SUV's in March with CO detectors.

The hope is to add an extra layer of protection for those who protect and serve.

ABC10 also contacted the Sacramento Police Department, Sacramento Sheriffs Department and CHP.

All said they do not have plans to add CO detectors to their vehicles.