The stain of Kali age, which insures to men sharp punishment in hell, is at once effaced by a single invocation of Hari.

Nama Article 22^nd July 2015

Source: Sahasranama Bhashya by Adi Sankara

कलिकल्मषमत्युग्र नरकार्त्तिप्रदं नृणाम् ।

प्रयाति विलयं सद्यः सकृदू यत्रानुसंस्मृते ।

The stain of Kali age, which insures to men sharp punishment in hell, is at once effaced by a single invocation of Hari.

Please check these: Excerpts from a discourse by our Sri Sri Muralidhara Swamiji

Is chanting while doing work considered as meaningful chanting ? 

Nama Chanted unknowingly also wipes out all of one's sins

Don't stop chanting for any reason. The rest of the things will be taken care of automatically.

Therefore, just as we bathe, wear clothes, eat food, etc. whether our mind is involved in it or not, so too, should we do a certain amount of Năma japa, părayana, kirtana, vandanam every day

Mechanical chanting is the only starting point we can attempt. It matures to love by grace.

Mechanical chanting is the starting phase. It will soon graduate to mental chanting and soon this mental one-pointed chanting will lead to the source of the chant, which is the truth.

Those who chant the Mahamantra even once in this Kali Yuga are assured of 'Moksha' (liberation)

It is impossible for anyone to do continuous Dhyana, Yoga or Brahma-Vichara or to observe austerities like fasting or vigil. But the Name can be chanted continuously even if it is mechanical.

Nama Kirtan, whether done knowingly or unknowingly, certainly has to give its effect

Japa even once uttered has its own good effect, whether the individual is aware or not.

The same scriptures also state that one should follow the words of the Guru without any doubts or questions and act accordingly.

Chant the Mahamantra Nama kirtan :

Hare Rama Hare Rama Rama Rama Hare Hare
Hare Krishna Hare Krishna Krishna Krishna Hare Hare