VX, the chemical used in the airport murder of Kim Jong Nam, is one of the deadliest chemical weapons ever created. The extremely toxic substance has been classified by the UN as a chemical weapon.

Malaysia police said on Friday that the authorities will sweep the international airport and other locations for radioactive material.

VX is outlawed under the Chemical Weapons Convention, except for "research, medical, or pharmaceutical purposes".

Here’s what we know about VX.

- VX is a nerve agent that is an oily liquid, and amber in color.

- VX is odorless and tasteless.

- VX is the most potent of all nerve agents.

Symptoms include blurred vision, coughing, headaches, and nausea in low doses, but can lead to paralysis, loss of consciousness, and respiratory failure in bigger amounts, according to the US government's Centers for Disease Control and Prevention (CDC).

The extent of poisoning caused by VX depends on how much a person was exposed to. Symptoms will start appearing either immediately or up to 18 hours later.

The sad thing is that people may not know they were exposed to VX because it has no odor.

As a kind of colorless and odorless oily liquid, VX turns into a gas the minute it is in contact with oxygen. It can be transmitted through air and water.

VX, if in vapor form, is the quickest and deadliest form of the killer gas. As a liquid, it could potentially be released into a water supply or used to poison someone's food.

It is not only the deadliest nerve agent, but also the most persistent in the environment. It evaporates slowly, especially in cold conditions, making it both a long- and short-term threat.

VX nerve gas was first developed in the UK in the 1950's as a deadly chemical warfare agent, according to CDC. 

CNN's military analyst Rick Francona says it was first used on the battlefield by the Iraqis, then later the Syrian government.

"Any country with a sophisticated chemical weapons effort can produce VX. The formula has been around since the 1950's, so it’s nothing new, it just has to be made, along with the political will and determination to build this weapon," Francona said.

Experts say the formula has been replicated in the past by the US, Russia, Syria and Iraq.

(With inputs from CNN, CDC)