diff --git a/src/models/slab_puff.jl b/src/models/slab_puff.jl
index d180f10..be7571e 100644
--- a/src/models/slab_puff.jl
+++ b/src/models/slab_puff.jl
@@ -128,7 +128,8 @@ function puff(scenario::Scenario, ::Type{SLAB}, eqs::EquationSet=DefaultSet();
                         AkimaInterpolation(out.cc.betax[tperm], out.cc.t[tperm]))
 end
 
-function puff(scenario::Scenario{<:AbstractSubstance,<:VerticalJet,<:Atmosphere}, ::Type{SLAB}, eqs::EquationSet=DefaultSet(); release_angle::Number=π/2, k2::Number=6.0, k3::Number=5.0)
+function puff(scenario::Scenario{<:AbstractSubstance,<:VerticalJet,<:Atmosphere}, ::Type{SLAB}, eqs::EquationSet=DefaultSet();
+              t_av=10, x_max=2000)
     c_max = 1.0
     stab = _slab_stab( _stability(scenario) )
     antoine = _slab_antoine(scenario)
@@ -167,14 +168,14 @@ function puff(scenario::Scenario{<:AbstractSubstance,<:VerticalJet,<:Atmosphere}
     xperm = sortperm(out.cc.x)
     tperm = sortperm(out.cc.t)
     return SLABSolution(scenario,:SLAB,inp,out,c_max,
-                        AkimaInterpolation(out.cc.cc, out.cc.x),
-                        AkimaInterpolation(out.cc.b, out.cc.x),
-                        AkimaInterpolation(out.cc.betac, out.cc.x),
-                        AkimaInterpolation(out.cc.zc, out.cc.x),
-                        AkimaInterpolation(out.cc.sig, out.cc.x),
-                        AkimaInterpolation(out.cc.xc, out.cc.t),
-                        AkimaInterpolation(out.cc.bx, out.cc.t),
-                        AkimaInterpolation(out.cc.betax, out.cc.t))
+                        AkimaInterpolation(out.cc.cc[xperm], out.cc.x[xperm]),
+                        AkimaInterpolation(out.cc.b[xperm], out.cc.x[xperm]),
+                        AkimaInterpolation(out.cc.betac[xperm], out.cc.x[xperm]),
+                        AkimaInterpolation(out.cc.zc[xperm], out.cc.x[xperm]),
+                        AkimaInterpolation(out.cc.sig[xperm], out.cc.x[xperm]),
+                        AkimaInterpolation(out.cc.xc[tperm], out.cc.t[tperm]),
+                        AkimaInterpolation(out.cc.bx[tperm], out.cc.t[tperm]),
+                        AkimaInterpolation(out.cc.betax[tperm], out.cc.t[tperm]))
 
 end
 
diff --git a/test/models/slab_tests.jl b/test/models/slab_tests.jl
index 541055d..dfa2d6e 100644
--- a/test/models/slab_tests.jl
+++ b/test/models/slab_tests.jl
@@ -273,4 +273,46 @@ end
     @test result ≈ out[:, 1:23]
 end
 
+@testset "INPR4 Vertical Jet - z0 = 1.0" begin
+    # this tests against the INPR4 test problem, but with the surface _surface_roughness
+    # at the default value for a SimpleAtmosphere type, z0=1.0
+
+    s = Substance(
+        name="inpr4",
+        molar_weight=0.070906,
+        gas_heat_capacity=498.1,
+        boiling_temp=239.1,
+        latent_heat=287840.0,
+        liquid_heat_capacity=926.3,
+        liquid_density=1574.0,
+        vapor_pressure=GasDispersion.Antoine(0,1978.34,-27.01)
+    )
+    r = VerticalJet(
+        fraction_liquid=0.88,
+        temperature=239.1,
+        mass_rate=3.33,
+        diameter=√(4*0.02/π),
+        duration=300.0,
+        height=1.0,
+        velocity=0.0,
+        pressure=101325
+    )
+
+    a = SimpleAtmosphere(
+        windspeed_height=10.0,
+        windspeed=1.0,
+        temperature=276.0,
+        rel_humidity=30.0,
+        stability=ClassD
+    )
+    tav = 1.0
+    xffm = 10000.0
+
+    inpr4 = Scenario(s,r,a)
+    rls = puff(inpr4, SLAB; t_av=tav, x_max=xffm)
+
+    @test rls.betax(17423.2) ≈ 4103.183379580039
+
+end
+
 end
\ No newline at end of file