MultiVapor TUTORIAL

Gerry Wood, March 18, 2007 

 (Tutorial Section One - Opening Window) 

 Welcome to the MultiVapor Tutorial. MultiVapor is a computer tool for estimating 

breakthrough times and service lives of air-purifying respirator cartridges 

manufactured to remove toxic organic vapors from breathed air. It can also be 

used for larger filters and for carbon beds of any size prepared for laboratory 

studies. MultiVapor replaces the program, Breakthrough, which performs the 

same function for only one organic vapor at all humidities. 

 A breakthrough time is the time following the first and continuous use of a 

cartridge after which the user of the cartridge could be exposed to a selected 

concentration of a harmful vapor. This is the consequence of the cartridge being 

used up. Service life is the breakthrough time with, possibly, a safety factor 

applied. 

 MultiVapor is intended to help an industrial hygienist or other qualified person to 

set cartridge change-out schedules. It is not a substitute for regulatory 

requirements or professional judgments. 

 Users must assume full responsibility for any application of the MultiVapor 

computer software. No warranties related to the software are expressed or 

implied by the National Institute for Occupational Safety and Health or its 

contractors. This software is intended to provide estimates based on the latest 

scientific information. The accuracies of any such estimates will depend in part 

on the accuracy and validity of the data entered by the user. 

 This tutorial will now guide us through the steps of using the MultiVapor 

computer program. We will see the windows as they appear when using the 

program and we will learn how to interact with those windows to enter the 

required data and get results. 

 Let’s begin by clicking on the [About] button in the upper left hand corner of this 

window. 

 (Tutorial Section Two – About Window) 

 The About window summarizes the research leading to the mathematical model 

and MultiVapor computer program. The basis and description of the model can 

be found in the publication cited here. 

 Now let's return to the opening window of the program by clicking on [Return]. 

 

 Pressing the [Continue] button takes us to the Data Input window. 
(Tutorial Section Three – Data Input Window) 

 This window shows the three categories of input information that are required to 

estimate a breakthrough time. 

 The first input category (in green) includes information about the respirator 

cartridge and the activated carbon it contains for removing organic vapors. 

 The second input category (in blue) includes information about the organic 

vapors of concern. 

 The third input category (in pink) includes data related to respirator use 

conditions. 

 

 Let's begin the data entry process by clicking on the [Organic Vapor Cartridge]

button which will take us to the Cartridge or Carbon Bed Data window. 

 

(Tutorial Section Four– Cartridge or Carbon Bed Data Window)

 The eight parameters that appear in this window are required to characterize 

the cartridge or carbon bed. They should be available from the cartridge, filter, or 

carbon manufacturer. After entering a cartridge description, the parameters can 

be entered and saved in the database for easy future retrieval by pressing [Save 

Entry in Database]. 

 The [Clear Data] button clears all fields and allows a new cartridge description 

and its parameters to be entered. 

 For this tutorial we've been provided with a set of sample cartridge 

parameters. They are saved in the program database under the cartridge name, 

“Typical OV Cartridge.” We choose this name from the drop-down list-box and 

press the [Search for Data] button to automatically fill all eight parameter fields. 

 To continue, we click on the [Return] button which takes us back to the Data 

Input window. 

 (Tutorial Section Five – Vapor Data Window) 

 

 Next, we need to specify the properties of the vapors. 

 

 Pressing [Organic Vapor #1] takes us to the Organic Vapor Data window. 

 We see that this window looks like the Cartridge or Carbon Bed Data window. 

User interactions in both windows work the same. The four buttons on the right 

all have the same labels and perform the same functions. 
 In the Organic Vapor Data window, we can select the first chemical vapor of 

concern from the drop-down list-box. Optionally, we could type in the chemical 

name in the box above or type its Chemical Abstract Services (CAS) number in 

the box below. A CAS number always has three numbers separated by dashes. 

 For this tutorial we select “Cyclohexane” from the chemical names by scrolling 

down the list-box past those chemicals with numerical prefixes. We need to be 

careful to avoid selecting a chemical with a similar name. 

 

 By pressing the [Search for Data] button, we can retrieve most of the data 

fields that are needed to estimate the breakthrough times. The CAS number is 

also displayed to confirm that the desired chemical has been selected. 

 As an exercise, let’s press [Clear Data] and search the database using the 

CAS number 110-82-7. The chemical name we get is “Hexanaphthene,” not 

“Cyclohexane.” Searching by a CAS number finds all the synonyms for the 

chemical name and inserts them in the list box. From the drop-down list-box, let's 

choose the name we prefer, “Cyclohexane.” 

 If we press [Return] at this point we get an error message saying we aren’t 

finished yet. Pressing [Return] in the Information Incomplete window takes us 

back to the Vapor Data window. 

 The blank data field relates to a condition that varies from workplace to 

workplace. Therefore, the database doesn't store a value for this. It’s the average 

concentration, in parts-per-million units, of vapor measured in the workplace. 

This value is best obtained by an industrial hygienist or other air-measurement 

expert. 

 For this tutorial, let’s enter 1200 parts-per-million as a sample measurement for 

cyclohexane. 

 We press [Return] to store the values for later calculations and take us back to 

the main Data Input window. 

 As we can see, the Data Input window now lists our cartridge and our first 

organic vapor. 

 MultiVapor has the capability of handling cases where there may be up to five 

organic vapors in the workplace. The other components of such mixtures in air 

are entered just as the first one was. The order of vapor entries doesn’t matter, 

but the program may change the order when it calculates results. 

 Let’s enter two more vapors: 500 parts-per-million of MIBK (methyl isobutyl 

ketone) and 800 parts-per-million toluene. 
 Returning to the Data Input window, we see the name of the cartridge and the 

three vapors we entered. 

 

 Now we need to specify the workplace environment itself. We press the [Use 

Conditions] button to take us to the Use Conditions window. 

(Tutorial Section Six– Use Conditions Window)

 It contains default values. These must be changed to reflect the actual 

temperature, atmospheric pressure, and relative humidity of the workplace 

environment. These values should be measured in the workplace with 

appropriate instruments. 

 The number of cartridges used with a particular respirator must be stated. This 

ranges from one or two cartridges for a negative-pressure, air-purifying respirator 

to up to five for a powered air-purifying respirator. 

 It’s also important to specify the average breathing rate. For example only, the 

chart at the bottom of the window describes typical breathing rates for various 

work efforts. However, the actual breathing rate depends upon the size and 

physical condition of the person using the respirator. Again, an industrial 

hygienist should be consulted to specify this parameter. 

 For our example we will use the default values and click the [Return] button.

 

 If we hadn’t visited and filled in all the input windows, we couldn’t proceed. 

Since we’ve done so, we can press the [Continue] button, which will take us to 

the final window. 

 (Tutorial Section Seven– Results Window) 

 The breakthrough time calculations now need one last category of data input. 

We must enter the breakthrough concentrations in parts per million in the 

appropriate boxes in this window. These values are the maximum concentrations 

the worker is allowed to breathe. They can be specified by a regulated standard, 

with or without a safety factor, or given as a professional judgment by an 

industrial hygienist. Let’s enter 300 for the allowable breakthrough concentration 

of cyclohexane, 100 for MIBK, and 200 for toluene. 

 At this point, if all the necessary parameters have been appropriately entered, 

pressing the [Calculate Results] button at the bottom of the window causes the 

program to complete the calculation. The program reports the answers for the 

estimated breakthrough times in the top right of the window. In this case we see 

estimated breakthrough times of 52 minutes for cyclohexane, 86 minutes for 

MIBK, and 107 minutes for toluene. 
 The calculation also provides lower and upper bounds for the breakthrough 

times to give an idea about the uncertainty of the answers. These range 

estimates are based upon model limitations and testing. They do not take into 

account incorrect input parameters. For our example, the breakthrough time 

range for cyclohexane is 42 to 63 minutes. 

 Another calculation can be done by pressing [Return to Data Inputs] to go 

back and change the cartridge, the vapors of concern, or the use 

conditions. Ultimately, four of the Use Condition parameters can be changed on 

the final window. For example, let's increase the relative humidity to 80 per cent. 

This reduces the cyclohexane time to 48 minutes. 

 This Results window can be printed by clicking on the [Print this Window]

button. 

 Notice the [Exit] buttons at the bottom of the Results window and in the Data 

Input window. They will terminate the program with the loss of results and any 

data that has not been saved in the databases with the [Save Entry in 

Database] buttons. However, a chance will be given to verify terminating the 

program. Let's confirm by pressing [Yes]. 

 This brings to an end the MultiVapor tutorial; we hope that this service life 

estimation computer program will be beneficial to you and your workers. Please 

contact us with any suggestions and comments so we can improve it.