The United States Postal Services processes and delivers 493.4 million mail pieces every day, which is an average of 20.6 million each hours, 342,638 per minute and 5,711 mail pieces that are processed every second.

With so much mail getting delivered, how does USPS ensure that each package and letter is safe?

National attention has been brought onto the stream of packages that include 12 possible pipe bombs to prominent political figures who were outspoken critics of President Donald Trump, such as former President Barack Obama, former Secretary of State Hillary Clinton, and news outlets such as CNN. A suspect in the mailing of the pipe bombs was arrested in Florida on Friday morning.

When asked about how the USPS screens packages for suspicious contents, Austin Postmaster Jason Berning declined to comment and referred the Austin Daily Herald to USPS media relations obtain further information.

A USPS spokesperson told the Herald that the entity developed a “comprehensive approach to protecting the mail system by utilizing a targeted strategy of specialized technology, screening protocols and employee training.”

To prevent attempts of compromising the entity’s investigation methods, the U.S. Postal Inspection Service doesn’t comment publicly on its procedures and operational protocols, the spokesperson said. However, USPS’ Postal Inspection Service organized response teams nationwide for investigating suspicious parcels through its Dangerous Mail Investigations (DMI) Program.

“DMI inspectors are trained to recognize the common characteristics of suspicious mail and are highly proficient in the use of state-of-the-art equipment to include portable x-ray machines,” the spokesperson said. “Any reports of suspicious mailings are taken very seriously, as they may impact the safety of postal employees and disrupt the process of mail.”

Characteristics and what to do

According to the U.S. Postal Inspection Service, the characteristics of suspicious parcels have repeatedly shown up that have helped letter carriers identify them. In 1991, a Dumfries, Virginia, letter carrier was able to identify a package in a collection box that was intended for the sender’s estranged husband and contained a bomb.

Some of these characteristics include:

Excessive postage. Usually, a bomber doesn’t want to mail a package over the county and have to work face-to-face with a window clerk.

The return address may be non-existent or fake.

The postmark shows a different location than the return address.

Mail bombs have restricted endorsements like “personal” or “private.” This is pretty significant when the addressee doesn’t usually get personal mail at the office.

Mail bombs may display distorted handwriting, or the name and address may be prepared with homemade labels or cut-and-paste lettering.

Package bombs may be unprofessionally wrapped with several combinations of tape to secure the package and may have endorsements like “Fragile-handle with care” or “Rush-do not delay.”

Letter bombs may feel rigid, or appear uneven or lopsided. Package bombs have a strange shape, soft spots or bulges.

Mail bombs might have protruding wires, aluminum foil, and oil stains, and may emit a weird smell.

“While the overwhelming volume of mail doesn’t permit the Postal Service to screen every piece, Postal Inspectors are able to respond quickly if a suspect article is discovered,” according to the U.S. Postal Inspection Service. “Each Inspection Service field division has trained and equipped bomb specialists available to provide professional assistance.”

If you are suspicious of a piece of mail and are unable to verify what’s inside, here’s what to do:

Don’t open the mail

Isolate the package and evacuate the immediate area

Don’t put in water or a confined space such as a desk drawer or cabinet

If possible, open windows in the immediate area to assist in venting potentially explosive gases

Don’t worry about being embarrassed if the item is proven to be safe. Contact the Postal Inspection Service and your local police department.

“We strive to provide a safe and secure mail system, preserve the integrity of the mail, and, most importantly, ensure a safe environment for postal employees, Postal Service customers, and the American public,” the USPS spokesperson added.