## Appendix A
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline
**Year** & **Instrument 1** & **Difference** & **Slope** & \(R^{2}\) & **Range** & **Points** & **Comment** & **Ref.** \\ \hline \multicolumn{1}{c}{Both FTIRs connected at the dilution tunnel} & & & & & & & \\
1985 & Prototype & - & 1.34 & 0.97 & 0.37 g/mi & 80 & G & [164] \\
1990 & Nicolet Sesam & 1.9\% (\(-2\)\%...1\%) & - & - & 0.2-0.9 g/mi & means & G, Dx2 & [165] \\
1990 & Mattson Horiba & - & 1.13 & 0.99 & 0.2-100 ppm & 25 & G (fuels, M85) & [112] \\  & & & Both FTIR and reference (FID) connected at the dilution tunnel & & & & \\
1990 & Nicolet Sesam & 17.6\% (\%\)(...38\%) & - & - & 0.2-0.9 g/mi & means & G, Dx2 & [165] \\
1996 & Nicolet REGA 7000 & \(-1\)\% & - & - & -10.00 ppm & cycles & G & [30] \\
2005 & _P. Tront Gasnet C72000_ & \(-6\)\%\(-63\)\% & - & - & 600 ppm & engine G, G & [110] \\
2006 & _P. Tront Gasnet CR2000_ & \(-5\)\% & 0.41 & 0.99 & 0.1-600 ppm & cycle & G & [163] \\  & & & & & & & \\ \multicolumn{1}{c}{FITR at the tulipple and reference at the dilution tunnel} & & & & & & \\
1994 & Nicolet REGA 7000 & 1.8\% (\(-4\)\%...4\%) & - & - & 50 ppm & 5 & CNG & [171] \\
1998 & VW Sesam & 1.09 & 0.97 & 0.4\% /mi & 65 & CNG10 & [113] \\
2000 & _P. Nicolet_ & 5\% & - & - & 500 mg/mi & 1 & G & [178] \\
2006 & _P. Tront Gasnet CR2000_ & \(-5\)\% (\(-5\)\%...4\%) & - & - & 160 mg/km & 10 & G & [163] \\
2018 & _P. Nicolet Analysis ICS_ & 4\% (\(-6\)\%...28\%) & 0.63 & 0.69 & 0.3-300 mg/km & 16 & D, CNG & [98] \\ \hline \multicolumn{1}{c}{\({}^{1}\)_P. portable (in italic)._} & & & & & & \\ \end{tabular}
\end{table} 
Table 10: Comparisons of FTIR with THC analyzers (FID). \begin{table}
\begin{tabular}{c c c c c c c c c} \hline
**Year** & **Instrument\({}^{\bf 1}\)** & **Difference** & **Slope** & \(\mathbf{R}^{2}\) & **Range** & **Points** & **Comment** & **Ref.** \\ \hline \multicolumn{8}{c}{FTIR measuring cylinder} \\
1992 & Nicolet REGA 7000 & 15\% & - & - & 15-17 ppm & 2 & Mix & [166] \\
2005 & _P-Tent Gamet C/2000_ & \(-\)51\% & - & - & 1509 ppm & 1 & & [101] \\
2015 & _P: Spectrum 2, Perkin Elmer_ & 1.0\% (\(-\)2.4\%\(\_\)7.1\%) & 1.02 & 1.00 & 0-50\% & 17 & & [181] \\ \multicolumn{8}{c}{Both FTIR corrected at the dilution tunnel (or tailpipe if specified)} \\
1991 & Bio-Rad Diglable FTS-60 & - & 0.89 & 0.96 & 0-10 ppm & 20 & Many G, fuels & [169] \\
1994 & Nicolet REGA 7000 & \(-\)17.9\% & - & - & 3 ppm & 1 & G (M85) & [171] \\
2016 & Thermo Fisher Antaris ICS & 2.4\% (0.8\%\(\_\)4.2\%) & - & - & 1500-3000 ppm & 12 & D-CNG & [167] \\ \multicolumn{8}{c}{FTIR at the tailpipe and reference at the dilution tunnel} \\
1998 & VV Seam & - & 1.09 & 0.99 & 0-07/gm\({}^{2}\) & 65 & C40 & [113] \\
2020 & AVL Seam & - & 0.96 & 0.99 & 0-04 mg/km\({}^{2}\) & 9 & D & [198] \\ \multicolumn{8}{c}{FTIR versus FTIR or GS} \\
1994 & Nicolet REGA 7000 \({}^{2}\) & 5\% & - & - & 43 ppm & 1 & CNG & [171] \\
1994 & Sesam II \({}^{5}\) & 5\% (\(-\)29\%\(\_\)20\%) & 1.11 & 0.99 & 40-250 ppm & 12 & G & [180] \\
2017 & Gasnet CR2000 \({}^{2}\) & - & 0.97 & 0.95 & 3-105 mg/km\({}^{2}\) & 17 & D2, G2, CNG & [197] \\
2020 & _P: Bruker Matrix MCS\({}^{3}\)_ & - & 1.07 & 0.93 & 0-600 ppm & cycle & D & [102] \\ \hline \multicolumn{8}{c}{\({}^{1}\)_P: portable (in italics): VS. GS \({}^{1}\)_vs. FTIR} \\ \hline \end{tabular}
\end{table} 
Table 6: Comparisons of FTIR with CH\({}_{4}\) analyzes (FID), unless specified otherwise.