## 3 Results
### TESEO Method (Technique to Estimate Operator's Errors)  
TESEO is an empirical method proposed by [PERSON] and [PERSON] in 1980 for estimating operator errors. It is one of the screening methods. It is the simplest of all methods for detecting human factor failure and requires the least material and capacity resources. In the TESEO method [29; 30] (Technica Stima Errori Operatori in Italian), the human error index is calculated according to the following formula:  
\[\text{P(E0)}=\text{K1.K2.K3.K4.K5} \tag{5}\]  
where:  
K1--the level of complexity of the task;  
K2--estimated time required to perform routine and non-routine activities of the operator;  
K3--training and experience of the operator;  
K4--stress index related to the seriousness of the situation;  
K5--interaction between the operator and the system. The values of the K indices are given in Table 3. The probability of an operator making a mistake is [21]:  
\[\text{P(EO)}=2^{\text{(n-1)}}.\text{P} \tag{6}\]  
where:  
P--the primary probability of making a mistake;  
n--the number of previous unsuccessful attempts to correct an incorrect decision. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Process** & \multicolumn{3}{c}{**HEP**} \\ \hline
**Step** & **Activity Description** & **Responsibility Person** & **Secondary Inspection** & **Technical Inspection** & **Resulting HEP** \\ \hline
18 & Bottle weighing & 0.003 & 0.001 & 0.001 & 0.00000003 \\ \hline
19 & Bottle and ramp valve closing & 0.001 & 0.001 & 0.001 & 0.00000001 \\ \hline
20 & Transport to the handling area & 0.001 & 0.001 & 0.001 & 0.00000001 \\ \hline
21 & Record in the production record & 0.001 & 0.001 & 0.001 & 0.00000001 \\ \hline
22 & Records of imported empty bottles, dispatched bottles and full bottles & 0.001 & 0.001 & 0.001 & 0.00000001 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: _Cont._ \begin{table}
\begin{tabular}{c} \hline \hline K1: Activity Typological Factor \\ \hline Simple, routine: 0.001 \\ Requiring attention, routine: 0.01 \\ Not routine: 0.1 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: TESEO method [29]. According to the Formula (6), the probability can reach a value of 1.0, which indicates that the operator was completely disoriented and completely lost control over the system. Table 4 shows the individual activities that are performed during the acetylene filling process. The parameters of the TESEO method (K1, K2, K3, K4 and K5) are identified for each activity. After estimating the parameters, the probability of failure of the human factor in individual activities was identified. The most risky activity in the acetylene filling process assessed by the TESEO method is the activity reacetonation and ramp degassing. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & **Process** & \multicolumn{4}{c}{**Factors**} & \multicolumn{1}{c}{**P**} \\ \hline
**Step** & **Activity Description** & **K1** & **K2** & **K3** & **K4** & **K5** & **(EO)** \\ \hline
1 & Empty bottles check & 0.001 & 0.5 & 1 & 1 & 7 & 0.0035 \\ \hline
2 & Checking the amount of solvent—acetone in the bottles & 0.001 & 0.5 & 1 & 1 & 7 & 0.0035 \\ \hline
3 & Reacetonation & 0.01 & 1 & 0.5 & 1 & 1 & 0.005 \\ \hline
4 & Connecting the bottles to filling points & 0.001 & 0.5 & 1 & 1 & 7 & 0.0035 \\ \hline
5 & Checking the tightness of connections & 0.001 & 1 & 0.5 & 1 & 3 & 0.0015 \\ \hline
6 & To be recorded in the production record & 0.001 & 0.5 & 1 & 1 & 7 & 0.0035 \\ of production & & & & & & & \\ \hline
7 & Securing bottles with fall-arrest chains & 0.001 & 1 & 0.5 & 1 & 3 & 0.0015 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Application of TESEO method for acetylene filling operation.