I work at a structural steel facility and currently we are welding together some support beams with 7/64 innershield.
As anyone who runs this wire or anything similar already knows, voltage porosity is a common occurrence unless welding parameters and technique are very precise.
I am aware that in the d1.1 there is a tolerance for voltage porosity, (whole size accumulated within x weld length etc...) and we have been welding this electrode to these standards for years.
We now have a new inspector who is telling us that no mater what the whole size is, if it contains slag, even in the smallest amount, it must be fixed because it is a "slag inclusion". Keep in mind, these are single pass fillet welds with very tiny wholes in random spots on random welds.
My understanding is this, first of all it's not a slag inclusion unless you weld over it. second, there are tolerances for slag inclusions depending on what your welding. third, this one is not "code book" but more just simple logic, if I were to take an acceptable sized voltage porosity whole, take a small enough piece of wire or whatever, and clean that slag out of the weld.... does it make it any stronger? I asked this inspector this very question and he said yes.
I can't seem to find anything in the d1.1 regarding slag in voltage porosity wholes. If anyone could refer me to something in the code book or similar source that goes a little more into detail I would appreciate it. Thanks.

The other posters have pretty well covered the subject.

Porosity itself is not the issue though should be brought under control to where it is a definite non-issue.

Slag remaining after slag removal procedures, usually from overlap or incomplete fusion.  Slag in porosity can get there from the needle scaler, chipping hammer, etc pounding it in but is not rejectable by any provision of Table 6.1 or anywhere in Clause 6.  Does not change the character of the porosity either.  Though, as stated by others, along a toe edge may add a new dimension to discerning fusion.  Rather grasping at straws I would say. 

I like the way you introduced new terminology.  Voltage porosity, I'll have to try and find a technical definition for that one though I can see how the two relate and could be contrasted with 'impurity porosity' or 'gaseous porosity' for instance.  Got our attention anyway and made us think.  Good going.

He Is In Control, Have a Great Day,  Brent

As anyone who runs this wire or anything similar already knows, voltage porosity is a common occurrence unless welding parameters and technique are very precise.

Seems like I recall something in FC 2002 for that. It was in the section covering the duties and responsibilities of the rice crispy whisperer.

Most of the welding in the shop is done with dual shield wire these days. The older guys in the shop are all capable of welding the inner shield without porosity. We only use the inner shield anymore on these support members and the majority of the problem is, they keep sticking rookies with the welding.
With time, the proper technique will be achieved and this won't be a problem but how much should we have to fix according to code in the meantime.
I hadn't realized that the term voltage porosity was more a general term invented by my peers. Kinda gave me a laugh.

Clause 6.9 "All welds shall be visually inspected and shall be acceptable if the criteria of Table 6.1 are satisfied"
This does not reference another source of visual acceptance criteria.

t

Table 6.1 is not all inclusive. Any inspector that hangs his future on table 6.1 without considering the visual criteria provided elsewhere in the code has a relative short future in the field of inspection.

Consider the following:

Clause 2 Design includes:
a) dimensional criteria for plus and slot welds.
b) criteria for checking the size of a fillet weld in a lap joint with regards to establishing the edge of the member.
c) hold back requirements.
d) end return requirements.
e) interrupting welds on opposite sides of a common plane.
f) removal of backing and weld tabs.
g) when members and how members of different thicknesses and widths must be transitioned.

Clause 3 Prequalification includes:
a) shape/contour of back gouges on the second side.
b) tolerances for prequalified groove details.
c) maximum root openings permitted without correction for members joined with fillet welds.

Clause 5 Fabrication includes
a) requirements electrode storage and exposure times (SMAW low hydrogen electrodes).
b) preheat and interpass temperatures.
c) WPS must be followed when making the weld.
d) heat input control for Q&T steels.
e) backing requirements, i.e., backing must be continuous and when more than one piece is joined to make a continuous backing, they must be CJP.
f) location of the weld in accordance with approved drawings.
g) mill induced defects (laps, seams, laminations).
h) acceptance criteria for laminations.
i) roughness requirements for thermal cut surfaces.
j) reentrant corners.
k) tack weld requirements.
l) Assembly tolerances.
m) separation between the underside of the groove and backing.
n) corrective actions for excessive root openings.
o) tolerances of stiffeners, compression members, etc.
p) Weld profiles including cracks, overlaps, face reinforcement, etc. 
q) repairs of typical defects including slag inclusions.
r) arc strikes.

I will agree that the New Farm Code includes no criteria for slag inclusions. Interesting. Could the inspector show you in the code where the discontinuity containing the slag was unacceptable?

How could it be that the New Farm Code does not include any criteria for slag inclusions?

Best regards - Al