Dell Inc. has assured users of its laptops that there is no danger from electrical jolts sometimes received from the cases of some of its systems.

Users have complained of receiving either a continuous electrical "tingling" or sharp shocks from some Dell laptops. The Dell machines involved include the 9400 and, more recently, laptops with brushed-aluminum cases, such as the XPS M1330 and XPS M1530.

In a knowledge base article published on Wednesday, Dell acknowledged that "a tingling sensation may be noticed when connecting devices to Dell notebook computers or printers and touching exposed metal parts of the devices being connected or the parent device." But Dell denied that the "tingling sensation" is cause for alarm and said the surges will neither harm human beings nor do any damage to the computer.

The jolts reported by some users are due to an electrical potential, or voltage, between exposed metal parts of the laptop and the earth, according to Dell. This voltage can be found in any electrical device powered by an AC adapter without an earth.

"The voltage does not present any risk of injury to the user," the company said.

Earlier this year, users began noticing the voltage issue with Dell 9400 laptops. Other Dell users have reported the same problem with notebooks such as the XPS M1530 and other notebooks with aluminum cases.

A voltage test by one user showed that the surface of the XPS M1530 was giving off more than 100 volts of power.

Users have said they could also feel the voltage when connecting cables or accessories.

Dell acknowledged that users might feel a "tingling sensation" but said that the voltage is harmless.

"If conditions are right for the human body to be more conductive, such as having wet hands or standing barefoot on a concrete floor, the probability of sensing the tingling (electric current) increases," Dell said in the knowledge base article. "It is recommended to unplug the AC adapter from the parent device before attaching any cables or accessories, as this reduces the possibility of experiencing the tingling sensation."

Some users who have complained of the tingles or shocks have been supplied with a three-pronged -- that is, earthed -- power adapter, which solves the problem.

Dell has been shipping two-prong (unearthed) power adapters with the majority of its systems worldwide for more than a year and a half, Dell's digital media manager, Lionel Menchaca, said in a forum post. As a result, the company isn't in a position to immediately supply all its customers with earthed adapters.

Dell is considering creating a program to   earthed power adapters to users at a discounted price, Menchaca said.

Electrical devices can be designed in such a way that they do not need a safety connection to electrical earth, normally by using reinforced insulation or having two layers of insulation.

Some users of non-Dell laptops, notably Apple Inc.'s aluminum-cased Mac laptops, have reported a similar tingling sensation.