On the nose of a stair you should not have the draught to take any dust through the carpet. This is something that happens through gaps in floor boards or under skirtings.
Peter
www.carpetcleanercardiff.com
Sorry have to disagree,
On the nose of a stair you will have as much if not more air flow
concentrated in that area for several reasons,
Most stairways direct warm air in an up wards direction faster than any where else in the house, most of this air will be soiled by cooking and dust, this air
will get trapped between the carpet and the underlay and in most cases it will be aided and abetted by the
wrong kind of underlay having been fitted to stairs.
Also hitting the carpet all day long will be the air and soil from doors being opened and closed continually, add to that the noses take the most impact and therefore soiling of any area in the home both front
and back by soiled air then Its little wonder that they suffer the most.
Air easily penetrates through the stairs from all angles be it from underneath through joins and floor boards or from the top through the gaps in the carpet left by fitting over the nosing, this creates a 'banjo' effect where the carpet just under the nosing does not reach the back sealing it off, we know this because we can , in most cases, bounce the carpet back of the riser at or just under the nosing down to the riser, lots of air gets trapped here.
Most fitters will use the the same underlay on the stairs as they have used through out the home and in most cases this will be waffle rubber, by its design the waffles is made to trap air in the pockets so of course it will trap soiled air and every time its stepped on this soiled air will be pressed out and it can only go through the backing and out before being sucked back in again which is the reason why the soil is in the lower pile and backing. By the way the cheaper the underlay used the bigger the waffle so more air is trapped so the potential for more soiling is there.
On stairs flat or crumb underlay should be used, years ago the wrong underlay specified and fitted was classed as a fitting fault.
To lessen the impact of soiling (in some cases its impossible to eradicate completely), on the stairs,gaps should be sealed before fitting the underlay ideally flat underlay should be fitted over the tread nosing and riser as
one piece.Sealing adds to cost which is why practically no one does it now.
When I have come across stairs that are soil saturated I can almost guarantee it will be because of one or a combination of these circumstances and pulling back the carpet generally confirms this, when brought to the attention of the home owner the explaination is generally accepted, the choice to go ahead then is theirs.
As a footnote I have seen carpets that have been fitted for less than two weeks affected by the above and had to be replaced.